wdiff rfc5545.original rfc5545.txt

Network Working Group B. Desruisseaux, Ed.
Internet-Draft
Request for Comments: 5545 Oracle
Obsoletes: 2445 (if approved) April 20, June 2009
Intended status:
Category: Standards Track
Expires: October 22, 2009

Internet Calendaring and Scheduling Core Object Specification
(iCalendar)
draft-ietf-calsify-rfc2445bis-10

Status of This Memo

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Abstract

This document defines the iCalendar data format for representing and
exchanging calendaring and scheduling information such as events, to-
dos, journal entries entries, and free/busy information, independent of any
particular calendar service or protocol.

Editorial Note (To be removed by RFC Editor prior to publication)

This document is a product of the Calendaring and Scheduling
Standards Simplification (Calsify) working group of the Internet
Engineering Task Force. Comments on this draft are welcomed, and
should be addressed to the ietf-calsify@osafoundation.org [1] mailing
list.

Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 8 5
2. Basic Grammar and Conventions . . . . . . . . . . . . . . . . 9 5
2.1. Formatting Conventions . . . . . . . . . . . . . . . . . 9 6
2.2. Related Memos . . . . . . . . . . . . . . . . . . . . . . 10 7
3. iCalendar Object Specification . . . . . . . . . . . . . . . 11 8
3.1. Content Lines . . . . . . . . . . . . . . . . . . . . . . 11 8
3.1.1. List and Field Separators . . . . . . . . . . . . . . 13 11
3.1.2. Multiple Values . . . . . . . . . . . . . . . . . . . 14 11
3.1.3. Binary Content . . . . . . . . . . . . . . . . . . . 14 11
3.1.4. Character Set . . . . . . . . . . . . . . . . . . . . 15 12
3.2. Property Parameters . . . . . . . . . . . . . . . . . . . 15 12
3.2.1. Alternate Text Representation . . . . . . . . . . . . 16 13
3.2.2. Common Name . . . . . . . . . . . . . . . . . . . . . 17 15
3.2.3. Calendar User Type . . . . . . . . . . . . . . . . . 18 15
3.2.4. Delegators . . . . . . . . . . . . . . . . . . . . . 19 16
3.2.5. Delegatees . . . . . . . . . . . . . . . . . . . . . 19 16
3.2.6. Directory Entry Reference . . . . . . . . . . . . . . 20 17
3.2.7. Inline Encoding . . . . . . . . . . . . . . . . . . . 20 17
3.2.8. Format Type . . . . . . . . . . . . . . . . . . . . . 21 18
3.2.9. Free/Busy Time Type . . . . . . . . . . . . . . . . . 22 19
3.2.10. Language . . . . . . . . . . . . . . . . . . . . . . 23 20
3.2.11. Group or List Membership . . . . . . . . . . . . . . 23 20
3.2.12. Participation Status . . . . . . . . . . . . . . . . 24 21
3.2.13. Recurrence Identifier Range . . . . . . . . . . . . . 25 22
3.2.14. Alarm Trigger Relationship . . . . . . . . . . . . . 26 23
3.2.15. Relationship Type . . . . . . . . . . . . . . . . . . 27 24
3.2.16. Participation Role . . . . . . . . . . . . . . . . . 28 25
3.2.17. RSVP Expectation . . . . . . . . . . . . . . . . . . 28 25
3.2.18. Sent By . . . . . . . . . . . . . . . . . . . . . . . 29 26
3.2.19. Time Zone Identifier . . . . . . . . . . . . . . . . 29 26
3.2.20. Value Data Types . . . . . . . . . . . . . . . . . . 31 28
3.3. Property Value Data Types . . . . . . . . . . . . . . . . 32 29
3.3.1. Binary . . . . . . . . . . . . . . . . . . . . . . . 32 29
3.3.2. Boolean . . . . . . . . . . . . . . . . . . . . . . . 33 30
3.3.3. Calendar User Address . . . . . . . . . . . . . . . . 33 30
3.3.4. Date . . . . . . . . . . . . . . . . . . . . . . . . 34 31
3.3.5. Date-Time . . . . . . . . . . . . . . . . . . . . . . 34 31
3.3.6. Duration . . . . . . . . . . . . . . . . . . . . . . 37 34
3.3.7. Float . . . . . . . . . . . . . . . . . . . . . . . . 38 35
3.3.8. Integer . . . . . . . . . . . . . . . . . . . . . . . 39 35
3.3.9. Period of Time . . . . . . . . . . . . . . . . . . . 39 36
3.3.10. Recurrence Rule . . . . . . . . . . . . . . . . . . . 40 37
3.3.11. Text . . . . . . . . . . . . . . . . . . . . . . . . 48 44
3.3.12. Time . . . . . . . . . . . . . . . . . . . . . . . . 49 46
3.3.13. URI . . . . . . . . . . . . . . . . . . . . . . . . . 51 48
3.3.14. UTC Offset . . . . . . . . . . . . . . . . . . . . . 52 48
3.4. iCalendar Object . . . . . . . . . . . . . . . . . . . . 53 49
3.5. Property . . . . . . . . . . . . . . . . . . . . . . . . 54 50
3.6. Calendar Components . . . . . . . . . . . . . . . . . . . 54 50
3.6.1. Event Component . . . . . . . . . . . . . . . . . . . 56 52
3.6.2. To-do To-Do Component . . . . . . . . . . . . . . . . . . . 60 56
3.6.3. Journal Component . . . . . . . . . . . . . . . . . . 62 58
3.6.4. Free/Busy Component . . . . . . . . . . . . . . . . . 64 60
3.6.5. Time Zone Component . . . . . . . . . . . . . . . . . 67 63
3.6.6. Alarm Component . . . . . . . . . . . . . . . . . . . 76 72
3.7. Calendar Properties . . . . . . . . . . . . . . . . . . . 81 77
3.7.1. Calendar Scale . . . . . . . . . . . . . . . . . . . 81 77
3.7.2. Method . . . . . . . . . . . . . . . . . . . . . . . 82 78
3.7.3. Product Identifier . . . . . . . . . . . . . . . . . 83 79
3.7.4. Version . . . . . . . . . . . . . . . . . . . . . . . 84 80
3.8. Component Properties . . . . . . . . . . . . . . . . . . 85 81
3.8.1. Descriptive Component Properties . . . . . . . . . . 85 81
3.8.1.1. Attachment . . . . . . . . . . . . . . . . . . . 85 81
3.8.1.2. Categories . . . . . . . . . . . . . . . . . . . 86 82
3.8.1.3. Classification . . . . . . . . . . . . . . . . . 87 83
3.8.1.4. Comment . . . . . . . . . . . . . . . . . . . . . 88 84
3.8.1.5. Description . . . . . . . . . . . . . . . . . . . 89 85
3.8.1.6. Geographic Position . . . . . . . . . . . . . . . 91 87
3.8.1.7. Location . . . . . . . . . . . . . . . . . . . . 92 88
3.8.1.8. Percent Complete . . . . . . . . . . . . . . . . 93 89
3.8.1.9. Priority . . . . . . . . . . . . . . . . . . . . 94 90
3.8.1.10. Resources . . . . . . . . . . . . . . . . . . . . 96 92
3.8.1.11. Status . . . . . . . . . . . . . . . . . . . . . 97 93
3.8.1.12. Summary . . . . . . . . . . . . . . . . . . . . . 98 94
3.8.2. Date and Time Component Properties . . . . . . . . . 100 95
3.8.2.1. Date/Time Date-Time Completed . . . . . . . . . . . . . . . 100 95
3.8.2.2. Date/Time Date-Time End . . . . . . . . . . . . . . . . . . 100 96
3.8.2.3. Date/Time Date-Time Due . . . . . . . . . . . . . . . . . . 102 97
3.8.2.4. Date/Time Date-Time Start . . . . . . . . . . . . . . . . . 103 99
3.8.2.5. Duration . . . . . . . . . . . . . . . . . . . . 104 100
3.8.2.6. Free/Busy Time . . . . . . . . . . . . . . . . . 105 101
3.8.2.7. Time Transparency . . . . . . . . . . . . . . . . 106 102
3.8.3. Time Zone Component Properties . . . . . . . . . . . 107 103
3.8.3.1. Time Zone Identifier . . . . . . . . . . . . . . 107 103
3.8.3.2. Time Zone Name . . . . . . . . . . . . . . . . . 109 105
3.8.3.3. Time Zone Offset From . . . . . . . . . . . . . . 110 106
3.8.3.4. Time Zone Offset To . . . . . . . . . . . . . . . 110 106
3.8.3.5. Time Zone URL . . . . . . . . . . . . . . . . . . 111 107
3.8.4. Relationship Component Properties . . . . . . . . . . 112 108
3.8.4.1. Attendee . . . . . . . . . . . . . . . . . . . . 112 108
3.8.4.2. Contact . . . . . . . . . . . . . . . . . . . . . 115 111
3.8.4.3. Organizer . . . . . . . . . . . . . . . . . . . . 117 113
3.8.4.4. Recurrence ID . . . . . . . . . . . . . . . . . . 118 114
3.8.4.5. Related To . . . . . . . . . . . . . . . . . . . 121 117
3.8.4.6. Uniform Resource Locator . . . . . . . . . . . . 122 118
3.8.4.7. Unique Identifier . . . . . . . . . . . . . . . . 123 119
3.8.5. Recurrence Component Properties . . . . . . . . . . . 124 120
3.8.5.1. Exception Date/Times Date-Times . . . . . . . . . . . . . . 124 120
3.8.5.2. Recurrence Date/Times Date-Times . . . . . . . . . . . . . . 126 122
3.8.5.3. Recurrence Rule . . . . . . . . . . . . . . . . . 128 124
3.8.6. Alarm Component Properties . . . . . . . . . . . . . 138 134
3.8.6.1. Action . . . . . . . . . . . . . . . . . . . . . 138 134
3.8.6.2. Repeat Count . . . . . . . . . . . . . . . . . . 139 135
3.8.6.3. Trigger . . . . . . . . . . . . . . . . . . . . . 139 135
3.8.7. Change Management Component Properties . . . . . . . 142 138
3.8.7.1. Date/Time Date-Time Created . . . . . . . . . . . . . . . . 142 138
3.8.7.2. Date/Time Date-Time Stamp . . . . . . . . . . . . . . . . . 143 139
3.8.7.3. Last Modified . . . . . . . . . . . . . . . . . . 144 140
3.8.7.4. Sequence Number . . . . . . . . . . . . . . . . . 145 141
3.8.8. Miscellaneous Component Properties . . . . . . . . . 146 142
3.8.8.1. IANA Properties . . . . . . . . . . . . . . . . . 146 142
3.8.8.2. Non-standard Non-Standard Properties . . . . . . . . . . . . . 146 142
3.8.8.3. Request Status . . . . . . . . . . . . . . . . . 148 144
4. iCalendar Object Examples . . . . . . . . . . . . . . . . . . 151 146
5. Recommended Practices . . . . . . . . . . . . . . . . . . . . 156 150
6. Internationalization Considerations . . . . . . . . . . . . . 157 151
7. Security Considerations . . . . . . . . . . . . . . . . . . . 158 151
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 159 151
8.1. iCalendar Media Type Registration . . . . . . . . . . . . 159 151
8.2. New iCalendar Elements Registration . . . . . . . . . . . 162 155
8.2.1. iCalendar Elements Registration Procedure . . . . . . 162 155
8.2.2. Registration Template for Components . . . . . . . . 162 155
8.2.3. Registration Template for Properties . . . . . . . . 163 156
8.2.4. Registration Template for Parameters . . . . . . . . 164 156
8.2.5. Registration Template for Value Data Types . . . . . 164 157
8.2.6. Registration Template for Values . . . . . . . . . . 164 157
8.3. Initial iCalendar Elements Registries . . . . . . . . . . 165 158
8.3.1. Components Registry . . . . . . . . . . . . . . . . . 165 158
8.3.2. Properties Registry . . . . . . . . . . . . . . . . . 166 158
8.3.3. Parameters Registry . . . . . . . . . . . . . . . . . 168 161
8.3.4. Value Data Types Registry . . . . . . . . . . . . . . 170 162
8.3.5. Calendar User Types Registry . . . . . . . . . . . . 170 162
8.3.6. Free/Busy Time Types Registry . . . . . . . . . . . . 171 163
8.3.7. Participation Statuses Registry . . . . . . . . . . . 171 163
8.3.8. Relationship Types Registry . . . . . . . . . . . . . 172 164
8.3.9. Participation Roles Registry . . . . . . . . . . . . 172 164
8.3.10. Actions Registry . . . . . . . . . . . . . . . . . . 173 165
8.3.11. Classifications Registry . . . . . . . . . . . . . . 173 165
8.3.12. Methods Registry . . . . . . . . . . . . . . . . . . 173 165
9. Acknowledgements Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 174 165
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 175 166
10.1. Normative References . . . . . . . . . . . . . . . . . . 175 166
10.2. Informative References . . . . . . . . . . . . . . . . . 176 167
Appendix A. Differences from RFC 2445 . . . . . . . . . . . . . 179 168
A.1. New restrictions Restrictions . . . . . . . . . . . . . . . . . . . . 179 169
A.2. Restrictions removed Removed . . . . . . . . . . . . . . . . . . 179 169
A.3. Deprecated features . . . . Features . . . . . . . . . . . . . . . 179
Appendix B. Change Log (to be removed by RFC Editor prior to
publication) . . . . . . . . . . . . . . . . . . . . 180
B.1. Changes in -10 . . . . . . . . . . . . . . . . . . . . . 180
B.2. Changes in -09 . . . . . . . . . . . . . . . . . . . . . 180
B.3. Changes in -08 . . . . . . . . . . . . . . . . . . . . . 181
B.4. Changes in -07 . . . . . . . . . . . . . . . . . . . . . 182
B.5. Changes in -06 . . . . . . . . . . . . . . . . . . . . . 183
B.6. Changes in -05 . . . . . . . . . . . . . . . . . . . . . 185
B.7. Changes in -04 . . . . . . . . . . . . . . . . . . . . . 185
B.8. Changes in -03 . . . . . . . . . . . . . . . . . . . . . 187
B.9. Changes in -02 . . . . . . . . . . . . . . . . . . . . . 187
B.10. Changes in -01 . . . . . . . . . . . . . . . . . . . . . 188 169

1. Introduction

The use of calendaring and scheduling has grown considerably in the
last decade. Enterprise and inter-enterprise business has become
dependent on rapid scheduling of events and actions using this
information technology. This memo is intended to progress the level
of interoperability possible between dissimilar calendaring and
scheduling applications. This memo defines a MIME content type for
exchanging electronic calendaring and scheduling information. The
Internet Calendaring and Scheduling Core Object Specification, or
iCalendar, allows for the capture and exchange of information
normally stored within a calendaring and scheduling application; such
as a Personal Information Manager (PIM) or a Group Scheduling Group-Scheduling
product.

The iCalendar format is suitable as an exchange format between
applications or systems. The format is defined in terms of a MIME
content type. This will enable the object to be exchanged using
several transports, including but not limited to SMTP, HTTP, a file
system, desktop interactive protocols such as the use of a memory-
based clipboard or drag/drop interactions, point-to-point
asynchronous communication, wired-network transport, or some form of
unwired transport such as infrared might also be used. infrared.

The memo also provides for the definition of iCalendar object methods
that will map this content type to a set of messages for supporting
calendaring and scheduling operations such as requesting, replying
to, modifying, and canceling meetings or appointments, to-dos to-dos, and
journal entries. The iCalendar object methods can be used to define
other calendaring and scheduling operations such a as requesting for
and replying with free/busy time data. Such a scheduling protocol is
defined in the iCalendar Transport-independent Interoperability
Protocol (iTIP) defined in [I-D.ietf-calsify-2446bis]. [2446bis].

The memo also includes a formal grammar for the content type based on
the Internet ABNF defined in [RFC5234]. This ABNF is required for
the implementation of parsers and to serve as the definitive
reference when ambiguities or questions arise in interpreting the
descriptive prose definition of the memo. Additional restrictions
that could not easily be expressed with the ABNF syntax are specified
as comments in the ABNF. Comments with normative statements should
be treated as such.

2. Basic Grammar and Conventions

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].

This memo makes use of both a descriptive prose and a more formal
notation for defining the calendaring and scheduling format.

The notation used in this memo is the ABNF notation of [RFC5234].
Readers intending on implementing the format defined in this memo
should be familiar with this notation in order to properly interpret
the specifications of this memo.

All numeric values used in this memo are given in decimal notation.

All names of properties, property parameters, enumerated property
values
values, and property parameter values are case-insensitive. However,
all other property values are case-sensitive, unless otherwise
stated.

Note: All indented editorial notes, such as this one, are intended
to provide the reader with additional information. The
information is not essential to the building of an implementation
conformant with this memo. The information is provided to
highlight a particular feature or characteristic of the memo.

The format for the iCalendar object is based on the syntax of the
text/directory media type [RFC2425]. While the iCalendar object is
not a profile of the text/directory media type [RFC2425], it does
reuse a number of the elements from the [RFC2425] specification.

2.1. Formatting Conventions

The elements defined in this memo are defined in prose. Many of the
terms used to describe these have common usage that is different than
the standards usage of this memo. In order to reference reference, within this
memo
memo, elements of the calendaring and scheduling model, core object
(this memo) memo), or interoperability protocol [I-D.ietf-calsify-2446bis] [2446bis] some formatting
conventions have been used. Calendaring and scheduling roles are
referred to in quoted-strings of text with the first character of
each word in upper case. uppercase. For example, "Organizer" refers to a role of
a "Calendar User" within the scheduling protocol defined by [I-D.ietf-calsify-2446bis].
[2446bis]. Calendar components defined by this memo are referred to
with capitalized, quoted-strings of text. All calendar components
start with the letter "V". For example, "VEVENT" refers to the event
calendar component, "VTODO" refers to the to-do calendar component component,
and "VJOURNAL" refers to the daily journal calendar component.
Scheduling methods defined by iTIP
[I-D.ietf-calsify-2446bis] [2446bis] are referred to with
capitalized, quoted-
strings quoted-strings of text. For example, "REQUEST" refers
to the method for requesting a scheduling calendar component be
created or modified, and "REPLY" refers to the method a recipient of
a request uses to update their status with the "Organizer" of the
calendar component.

The properties defined by this memo are referred to with capitalized,
quoted-strings of text, followed by the word "property". For
example, "ATTENDEE" property refers to the iCalendar property used to
convey the calendar address of a calendar user. Property parameters
defined by this memo are referred to with lowercase, quoted-strings
of text, followed by the word "parameter". For example, "value"
parameter refers to the iCalendar property parameter used to override
the default value type for a property value. Enumerated values
defined by this memo are referred to with capitalized text, either
alone or followed by the word "value". For example, the "MINUTELY"
value can be used with the "FREQ" component of the "RECUR" value type
to specify repeating components based on an interval of one minute or
more.

In this document, descriptions of characters are of

The following table lists the form
"character name (codepoint)", where "codepoint" is different characters from the US-ASCII
[US-ASCII] character set. The "character name" set that is referenced in this document. For
each character, the table specifies the authoritative
description; (codepoint) is a reference to that character in US-
ASCII. name used
throughout this document, along with its US-ASCII decimal codepoint.

+------------------------+-------------------+
| Character name | Decimal codepoint |
+------------------------+-------------------+
| HTAB | 9 |
| LF | 10 |
| CR | 13 |
| DQUOTE | 22 |
| SPACE | 32 |
| PLUS SIGN | 43 |
| COMMA | 44 |
| HYPHEN-MINUS | 45 |
| PERIOD | 46 |
| SOLIDUS | 47 |
| COLON | 58 |
| SEMICOLON | 59 |
| LATIN CAPITAL LETTER N | 78 |
| LATIN CAPITAL LETTER T | 84 |
| LATIN CAPITAL LETTER X | 88 |
| LATIN CAPITAL LETTER Z | 90 |
| BACKSLASH | 92 |
| LATIN SMALL LETTER N | 110 |
+------------------------+-------------------+

2.2. Related Memos

Implementers will need to be familiar with several other memos that,
along with this memo, form a framework for Internet calendaring and
scheduling standards. This memo specifies a core specification of
objects, value types, properties properties, and property parameters.

o iTIP [I-D.ietf-calsify-2446bis] [2446bis] specifies an interoperability protocol for
scheduling between different implementations;

o iMIP [I-D.ietf-calsify-rfc2447bis] iCalendar Message-Based Interoperability Protocol (iMIP) [2447bis]
specifies an Internet email binding for [I-D.ietf-calsify-2446bis]. [2446bis].

This memo does not attempt to repeat the specification of concepts or
definitions from these other memos. Where possible, references are
made to the memo that provides for the specification of these
concepts or definitions.

3. iCalendar Object Specification

The following sections define the details of a Calendaring and
Scheduling Core Object Specification. The Calendaring and Scheduling
Core Object is a collection of calendaring and scheduling
information. Typically, this information will consist of an
iCalendar stream with one or more iCalendar objects. The body of the
iCalendar object consists of a sequence of calendar properties and
one or more calendar components.

Section 3.1 defines the content line format; Section 3.2 defines the
property parameter format; Section 3.3 defines the data types for
property values; Section 3.4 defines the iCalendar object format;
Section 3.5 defines the iCalendar property format; Section 3.6
defines the calendar component format; Section 3.7 defines calendar
properties; and Section 3.8 defines calendar component properties.

This information is intended to be an integral part of the MIME
content type registration. In addition, this information can be used
independent of such content registration. In particular, this memo
has direct applicability for use as a calendaring and scheduling
exchange format in file-, memory- memory-, or network-based transport
mechanisms.

3.1. Content Lines

The iCalendar object is organized into individual lines of text,
called content lines. Content lines are delimited by a line break,
which is a CRLF sequence (US-ASCII decimal 13, (CR character followed by US-ASCII
decimal 10). LF character).

Lines of text SHOULD NOT be longer than 75 octets, excluding the line
break. Long content lines SHOULD be split into a multiple line
representations using a line "folding" technique. That is, a long
line can be split between any two characters by inserting a CRLF
immediately followed by a single linear white space white-space character (i.e.,
SPACE, US-ASCII decimal 32
SPACE or HTAB, US-ASCII decimal 9). HTAB). Any sequence of CRLF followed immediately by a
single linear white space white-space character is ignored (i.e., removed) when
processing the content type.

For example example, the line:

DESCRIPTION:This is a long description that exists on a long line.

Can be represented as:

DESCRIPTION:This is a lo
ng description
that exists on a long line.

The process of moving from this folded multiple line multiple-line representation
to its single line single-line representation is called "unfolding". Unfolding
is accomplished by removing the CRLF character and the linear white
space white-space
character that immediately follows.

When parsing a content line, folded lines MUST first be unfolded
according to the unfolding procedure described above.

Note: It is possible for very simple implementations to generate
improperly folded lines in the middle of a UTF-8 multi-octet
sequence. For this reason, implementations need to unfold lines
in such a way to properly restore the original sequence.

The content information associated with an iCalendar object is
formatted using a syntax similar to that defined by [RFC2425]. That
is, the content information consists of CRLF-separated content lines.

The following notation defines the lines of content in an iCalendar
object:

contentline = name *(";" param ) ":" value CRLF
; This ABNF is just a general definition for an initial parsing
; of the content line into its property name, parameter list,
; and value string

; When parsing a content line, folded lines MUST first
; be unfolded according to the unfolding procedure
; described above. When generating a content line, lines
; longer than 75 octets SHOULD be folded according to
; the folding procedure described above.

name = iana-token / x-name

iana-token = 1*(ALPHA / DIGIT / "-")
; iCalendar identifier registered with IANA
x-name = "X-" [vendorid "-"] 1*(ALPHA / DIGIT / "-")
; Reserved for experimental use.

vendorid = 3*(ALPHA / DIGIT)
; Vendor identification

param = param-name "=" param-value *("," param-value)
; Each property defines the specific ABNF for the parameters
; allowed on the property. Refer to specific properties for
; precise parameter ABNF.

param-name = iana-token / x-name

param-value = paramtext / quoted-string

paramtext = *SAFE-CHAR

value = *VALUE-CHAR

quoted-string = DQUOTE *QSAFE-CHAR DQUOTE

QSAFE-CHAR = WSP / %x21 / %x23-7E / NON-US-ASCII
; Any character except CONTROL and DQUOTE

SAFE-CHAR = WSP / %x21 / %x23-2B / %x2D-39 / %x3C-7E
/ NON-US-ASCII
; Any character except CONTROL, DQUOTE, ";", ":", ","

VALUE-CHAR = WSP / %x21-7E / NON-US-ASCII
; Any textual character

NON-US-ASCII = UTF8-2 / UTF8-3 / UTF8-4
; UTF8-2, UTF8-3, and UTF8-4 are defined in [RFC3629]

CONTROL = %x00-08 / %x0A-1F / %x7F
; All the controls except HTAB

The property value component of a content line has a format that is
property specific. Refer to the section describing each property for
a definition of this format.

All names of properties, property parameters, enumerated property
values and property parameter values are case-insensitive. However,
all other property values are case-sensitive, unless otherwise
stated.

3.1.1. List and Field Separators

Some properties and parameters allow a list of values. Values in a
list of values MUST be separated by a COMMA character (US-ASCII
decimal 44). character. There is no
significance to the order of values in a list. For those parameter
values (such as those that specify URI values) that are specified in
quoted-strings, the individual quoted-
strings quoted-strings are separated by a
COMMA character (US-ASCII decimal 44). character.

Some property values are defined in terms of multiple parts. These
structured property values MUST have their value parts separated by a
SEMICOLON character (US-ASCII decimal 59). character.

Some properties allow a list of parameters. Each property parameter
in a list of property parameters MUST be separated by a SEMICOLON
character (US-ASCII decimal 59).
character.

Property parameters with values containing a COLON character (US-
ASCII decimal 58), character, a
SEMICOLON character (US-ASCII decimal 59) or a COMMA character (US-ASCII decimal 44) MUST be placed in quoted
text.

For example, in the following properties properties, a SEMICOLON is used to
separate property parameters from each other, other and a COMMA character is
used to separate property values in a value list.

ATTENDEE;RSVP=TRUE;ROLE=REQ-PARTICIPANT:mailto:
jsmith@example.com

RDATE;VALUE=DATE:19970304,19970504,19970704,19970904

3.1.2. Multiple Values

Some properties defined in the iCalendar object can have multiple
values. The general rule for encoding multi-valued items is to
simply create a new content line for each value, including the
property name. However, it should be noted that some properties
support encoding multiple values in a single property by separating
the values with a COMMA character (US-ASCII decimal 44). character. Individual property definitions
should be consulted for determining whether a specific property
allows multiple values and in which of these two forms. Multi-valued
properties MUST NOT be used to specify multiple language variants of
the same value. Calendar applications SHOULD display all values.

3.1.3. Binary Content

Binary content information in an iCalendar object SHOULD be
referenced using a URI within a property value. That is is, the binary
content information SHOULD be placed in an external MIME entity that
can be referenced by a URI from within the iCalendar object. In
applications where this is not feasible, binary content information
can be included within an iCalendar object, but only after first
encoding it into text using the "BASE64" encoding method defined in
[RFC4648]. Inline binary content SHOULD only be used in applications
whose special circumstances demand that an iCalendar object be
expressed as a single entity. A property containing inline binary
content information MUST specify the "ENCODING" property parameter.
Binary content information placed external to the iCalendar object
MUST be referenced by a uniform resource identifier (URI).

The following example specifies an "ATTACH" property that references
an attachment external to the iCalendar object with a URI reference:

ATTACH:http://example.com/public/quarterly-report.doc

The following example specifies an "ATTACH" property with inline
binary encoded content information:

ATTACH;FMTTYPE=text/plain;ENCODING=BASE64;VALUE=BINARY:VGhlIH
F1aWNrIGJyb3duIGZveCBqdW1wcyBvdmVyIHRoZSBsYXp5IGRvZy4

3.1.4. Character Set

There is not a property parameter to declare the charset used in a
property value. The default charset for an iCalendar stream is UTF-8
as defined in [RFC3629].

The "charset" Content-Type parameter MUST be used in MIME transports
to specify the charset being used.

3.2. Property Parameters

A property can have attributes associated with it. which it is associated. These
"property parameters" contain meta-information about the property or
the property value. Property parameters are provided to specify such
information as the location of an alternate text representation for a
property value, the language of a text property value, the value type
of the property value value, and other attributes.

Property parameter values that contain the COLON (US-ASCII decimal
58), SEMICOLON (US-ASCII decimal 59) COLON, SEMICOLON, or COMMA (US-ASCII decimal 44)
character separators MUST be specified as quoted-string text values.
Property parameter values MUST NOT contain the DQUOTE (US-ASCII
decimal 22) character. The
DQUOTE (US-ASCII decimal 22) character is used as a delimiter for parameter values that
contain restricted characters or URI text. For example:

DESCRIPTION;ALTREP="cid:part1.0001@example.org":The Fall'98 Wild
Wizards Conference - - Las Vegas\, NV\, USA
Property parameter values that are not in quoted strings quoted-strings are case case-
insensitive.

The general property parameters defined by this memo are defined by
the following notation:

icalparameter = altrepparam ; Alternate text representation
/ cnparam ; Common name
/ cutypeparam ; Calendar user type
/ delfromparam ; Delegator
/ deltoparam ; Delegatee
/ dirparam ; Directory entry
/ encodingparam ; Inline encoding
/ fmttypeparam ; Format type
/ fbtypeparam ; Free/busy time type
/ languageparam ; Language for text
/ memberparam ; Group or list membership
/ partstatparam ; Participation status
/ rangeparam ; Recurrence identifier range
/ trigrelparam ; Alarm trigger relationship
/ reltypeparam ; Relationship type
/ roleparam ; Participation role
/ rsvpparam ; RSVP expectation
/ sentbyparam ; Sent by
/ tzidparam ; Reference to time zone object
/ valuetypeparam ; Property value data type
/ other-param

other-param = (iana-param / x-param)

iana-param = iana-token "=" param-value *("," param-value)
; Some other IANA registered IANA-registered iCalendar parameter.

x-param = x-name "=" param-value *("," param-value)
; A non-standard, experimental parameter.

Applications MUST ignore x-param and iana-param value values they don't
recognized.
recognize.

3.2.1. Alternate Text Representation

Parameter Name: ALTREP

Purpose: To specify an alternate text representation for the
property value.

Format Definition: This property parameter is defined by the
following notation:

altrepparam = "ALTREP" "=" DQUOTE uri DQUOTE

Description: This parameter specifies a URI that points to an
alternate representation for a textual property value. A property
specifying this parameter MUST also include a value that reflects
the default representation of the text value. The URI parameter
value MUST be specified in a quoted-string.

Note: While there is no restriction imposed on the URI schemes
allowed for this parameter, CID Content Identifier (CID) [RFC2392],
HTTP [RFC2616], and HTTPS [RFC2818] are the URI schemes most
commonly used by current implementations.

Example:

DESCRIPTION;ALTREP="CID:part3.msg.970415T083000@example.com":
Project XYZ Review Meeting will include the following agenda
items: (a) Market Overview\, (b) Finances\, (c) Project Man
agement

The "ALTREP" property parameter value might point to a "text/html"
content portion.

Content-Type:text/html
Content-Id:<part3.msg.970415T083000@example.com>

<html>
<head>
<title></title>
</head>
<body>
<p>
<b>Project XYZ Review Meeting</b> will include
the following agenda items:
<ol>
<li>Market Overview</li>
<li>Finances</li>
<li>Project Management</li>
</ol>
</p>
</body>
</html>

3.2.2. Common Name

Parameter Name: CN

Purpose: To specify the common name to be associated with the
calendar user specified by the property.

Format Definition: This property parameter is defined by the
following notation:

cnparam = "CN" "=" param-value

Description: This parameter can be specified on properties with a
CAL-ADDRESS value type. The parameter specifies the common name
to be associated with the calendar user specified by the property.
The parameter value is text. The parameter value can be used for
display text to be associated with the calendar address specified
by the property.

Example:

ORGANIZER;CN="John Smith":mailto:jsmith@example.com

3.2.3. Calendar User Type

Parameter Name: CUTYPE

Purpose: To specify identify the type of calendar user specified by the
property.

Format Definition: This property parameter is defined by the
following notation:

cutypeparam = "CUTYPE" "="
("INDIVIDUAL" ; An individual
/ "GROUP" ; A group of individuals
/ "RESOURCE" ; A physical resource
/ "ROOM" ; A room resource
/ "UNKNOWN" ; Otherwise not known
/ x-name ; Experimental type
/ iana-token) ; Other IANA registered IANA-registered
; type
; Default is INDIVIDUAL
Description: This parameter can be specified on properties with a
CAL-ADDRESS value type. The parameter identifies the type of
calendar user specified by the property. If not specified on a
property that allows this parameter, the default is INDIVIDUAL.
Applications MUST treat x-name and iana-token value values they don't
recognized
recognize the same way as they would the UNKNOWN value.

Example:

ATTENDEE;CUTYPE=GROUP:mailto:ietf-calsch@example.org

3.2.4. Delegators

Parameter Name: DELEGATED-FROM

Purpose: To specify the calendar users that have delegated their
participation to the calendar user specified by the property.

Format Definition: This property parameter is defined by the
following notation:

delfromparam = "DELEGATED-FROM" "=" DQUOTE cal-address
DQUOTE *("," DQUOTE cal-address DQUOTE)

Description: This parameter can be specified on properties with a
CAL-ADDRESS value type. This parameter specifies those calendar
users that have delegated their participation in a group scheduled group-scheduled
event or to-do to the calendar user specified by the property.
The individual calendar address parameter values MUST each be
specified in a quoted-string.

Example:

ATTENDEE;DELEGATED-FROM="mailto:jsmith@example.com":mailto:
jdoe@example.com

3.2.5. Delegatees

Parameter Name: DELEGATED-TO

Purpose: To specify the calendar users to whom the calendar user
specified by the property has delegated participation.

Format Definition: This property parameter is defined by the
following notation:

deltoparam = "DELEGATED-TO" "=" DQUOTE cal-address DQUOTE
*("," DQUOTE cal-address DQUOTE)
Description: This parameter can be specified on properties with a
CAL-ADDRESS value type. This parameter specifies those calendar
users whom have been delegated participation in a group scheduled group-scheduled
event or to-do by the calendar user specified by the property.
The individual calendar address parameter values MUST each be
specified in a quoted-string.

Example:

ATTENDEE;DELEGATED-TO="mailto:jdoe@example.com","mailto:jqpublic
@example.com":mailto:jsmith@example.com

3.2.6. Directory Entry Reference

Parameter Name: DIR

Purpose: To specify reference to a directory entry associated with
the calendar user specified by the property.

Format Definition: This property parameter is defined by the
following notation:

dirparam = "DIR" "=" DQUOTE uri DQUOTE

Description: This parameter can be specified on properties with a
CAL-ADDRESS value type. The parameter specifies a reference to
the directory entry associated with the calendar user specified by
the property. The parameter value is a URI. The URI parameter
value MUST be specified in a quoted-string.

Note: While there is no restriction imposed on the URI schemes
allowed for this parameter, CID [RFC2392], DATA [RFC2397], FILE
[RFC1738], FTP [RFC1738], HTTP [RFC2616], HTTPS [RFC2818], LDAP
[RFC4516], and MID [RFC2392] are the URI schemes most commonly
used by current implementations.

Example:

ORGANIZER;DIR="ldap://example.com:6666/o=ABC%20Industries,
c=US???(cn=Jim%20Dolittle)":mailto:jimdo@example.com

3.2.7. Inline Encoding

Parameter Name: ENCODING
Purpose: To specify an alternate inline encoding for the property
value.

Format Definition: This property parameter is defined by the
following notation:

encodingparam = "ENCODING" "="
( "8BIT"
; "8bit" text encoding is defined in [RFC2045]
/ "BASE64"
; "BASE64" binary encoding format is defined in [RFC4648]
)

Description: This property parameter identifies the inline encoding
used in a property value. The default encoding is "8BIT",
corresponding to a property value consisting of text. The
"BASE64" encoding type corresponds to a property value encoded
using the "BASE64" encoding defined in [RFC2045].

If the value type parameter is ";VALUE=BINARY", then the inline
encoding parameter MUST be specified with the value
";ENCODING=BASE64".

Example:

ATTACH;FMTTYPE=text/plain;ENCODING=BASE64;VALUE=BINARY:TG9yZW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3.2.8. Format Type

Parameter Name: FMTTYPE

Purpose: To specify the content type of a referenced object.

Format Definition: This property parameter is defined by the
following notation:

fmttypeparam = "FMTTYPE" "=" type-name "/" subtype-name
; Where "type-name" and "subtype-name" are
; defined in section Section 4.2 of [RFC4288] [RFC4288].

Description: This parameter can be specified on properties that are
used to reference an object. The parameter specifies the media
type [RFC4288] of the referenced object. For example, on the
"ATTACH" property, a an FTP type URI value does not, by itself,
necessarily convey the type of content associated with the
resource. The parameter value MUST be the text for either an IANA
registered
IANA-registered media type or a non-standard media type.

Example:

ATTACH;FMTTYPE=application/msword:ftp://example.com/pub/docs/
agenda.doc

3.2.9. Free/Busy Time Type

Parameter Name: FBTYPE

Purpose: To specify the free or busy time type.

Format Definition: This property parameter is defined by the
following notation:

fbtypeparam = "FBTYPE" "=" ("FREE" / "BUSY"
/ "BUSY-UNAVAILABLE" / "BUSY-TENTATIVE"
/ x-name
; Some experimental iCalendar free busy free/busy type.
/ iana-token)
; Some other IANA registered IANA-registered iCalendar free busy free/busy type.

Description: This parameter specifies the free or busy time type.
The value FREE indicates that the time interval is free for
scheduling. The value BUSY indicates that the time interval is
busy because one or more events have been scheduled for that
interval. The value BUSY-UNAVAILABLE indicates that the time
interval is busy and that the interval can not be scheduled. The
value BUSY-TENTATIVE indicates that the time interval is busy
because one or more events have been tentatively scheduled for
that interval. If not specified on a property that allows this
parameter, the default is BUSY. Applications MUST treat x-name
and iana-token value values they don't recognized recognize the same way as they
would the BUSY value.

Example: The following is an example of this parameter on a
"FREEBUSY" property.

FREEBUSY;FBTYPE=BUSY:19980415T133000Z/19980415T170000Z

3.2.10. Language

Parameter Name: LANGUAGE

Purpose: To specify the language for text values in a property or
property parameter.

Format Definition: This property parameter is defined by the
following notation:

languageparam = "LANGUAGE" "=" language

language = Language-Tag
; As defined in [RFC4646] [RFC4646].

Description: This parameter identifies the language of the text in
the property value and of all property parameter values of the
property. The value of the "LANGUAGE" property parameter is that
defined in [RFC4646].

For transport in a MIME entity, the Content-Language header field
can be used to set the default language for the entire body part.
Otherwise, no default language is assumed.

Example: The following are examples of this parameter on the
"SUMMARY" and "LOCATION" properties:

SUMMARY;LANGUAGE=en-US:Company Holiday Party

LOCATION;LANGUAGE=en:Germany

LOCATION;LANGUAGE=no:Tyskland

3.2.11. Group or List Membership

Parameter Name: MEMBER

Purpose: To specify the group or list membership of the calendar
user specified by the property.

Format Definition: This property parameter is defined by the
following notation:

memberparam = "MEMBER" "=" DQUOTE cal-address DQUOTE
*("," DQUOTE cal-address DQUOTE)
Description: This parameter can be specified on properties with a
CAL-ADDRESS value type. The parameter identifies the groups or
list membership for the calendar user specified by the property.
The parameter value is either a single calendar address in a
quoted-string or a COMMA character (US-ASCII decimal 44) separated COMMA-separated list of calendar addresses,
each in a quoted-string. The individual calendar address
parameter values MUST each be specified in a quoted-string.

Example:

ATTENDEE;MEMBER="mailto:ietf-calsch@example.org":mailto:
jsmith@example.com

ATTENDEE;MEMBER="mailto:projectA@example.com","mailto:pr
ojectB@example.com":mailto:janedoe@example.com

3.2.12. Participation Status

Parameter Name: PARTSTAT

Purpose: To specify the participation status for the calendar user
specified by the property.

Format Definition: This property parameter is defined by the
following notation:

partstatparam = "PARTSTAT" "="
(partstat-event
/ partstat-todo
/ partstat-jour)

partstat-event = ("NEEDS-ACTION" ; Event needs action
/ "ACCEPTED" ; Event accepted
/ "DECLINED" ; Event declined
/ "TENTATIVE" ; Event tentatively
; accepted
/ "DELEGATED" ; Event delegated
/ x-name ; Experimental status
/ iana-token) ; Other IANA registered IANA-registered
; status
; These are the participation statuses for a "VEVENT".
; Default is NEEDS-ACTION.

partstat-todo = ("NEEDS-ACTION" ; To-do needs action
/ "ACCEPTED" ; To-do accepted
/ "DECLINED" ; To-do declined
/ "TENTATIVE" ; To-do tentatively
; accepted
/ "DELEGATED" ; To-do delegated
/ "COMPLETED" ; To-do completed. completed
; COMPLETED property has
; date/time completed. DATE-TIME completed
/ "IN-PROCESS" ; To-do in process of
; being completed
/ x-name ; Experimental status
/ iana-token) ; Other IANA registered IANA-registered
; status
; These are the participation statuses for a "VTODO".
; Default is NEEDS-ACTION.

partstat-jour = ("NEEDS-ACTION" ; Journal needs action
/ "ACCEPTED" ; Journal accepted
/ "DECLINED" ; Journal declined
/ x-name ; Experimental status
/ iana-token) ; Other IANA registered IANA-registered
; status
; These are the participation statuses for a "VJOURNAL".
; Default is NEEDS-ACTION.

Description: This parameter can be specified on properties with a
CAL-ADDRESS value type. The parameter identifies the
participation status for the calendar user specified by the
property value. The parameter values differ depending on whether
they are associated with a group scheduled group-scheduled "VEVENT", "VTODO" "VTODO", or
"VJOURNAL". The values MUST match one of the values allowed for
the given calendar component. If not specified on a property that
allows this parameter, the default value is NEEDS-ACTION.
Applications MUST treat x-name and iana-token value values they don't
recognized
recognize the same way as they would the NEEDS-ACTION value.

Example:

ATTENDEE;PARTSTAT=DECLINED:mailto:jsmith@example.com

3.2.13. Recurrence Identifier Range
Parameter Name: RANGE

Purpose: To specify the effective range of recurrence instances from
the instance specified by the recurrence identifier specified by
the property.

Format Definition: This property parameter is defined by the
following notation:

rangeparam = "RANGE" "=" "THISANDFUTURE"
; To specify the instance specified by the recurrence identifier
; and all subsequent recurrence instances instances.

Description: This parameter can be specified on a property that
specifies a recurrence identifier. The parameter specifies the
effective range of recurrence instances that is specified by the
property. The effective range is from the recurrence identifier
specified by the property. If this parameter is not specified on
an allowed property, then the default range is the single instance
specified by the recurrence identifier value of the property. The
parameter value can only be "THISANDFUTURE" to indicate a range
defined by the recurrence identifier and all subsequent instances.
The value "THISANDPRIOR" is deprecated by this revision of
iCalendar and MUST NOT be generated by applications.

Example:

RECURRENCE-ID;RANGE=THISANDFUTURE:19980401T133000Z

3.2.14. Alarm Trigger Relationship

Parameter Name: RELATED

Purpose: To specify the relationship of the alarm trigger with
respect to the start or end of the calendar component.

Format Definition: This property parameter is defined by the
following notation:

trigrelparam = "RELATED" "="
("START" ; Trigger off of start
/ "END") ; Trigger off of end

Description: This parameter can be specified on properties that
specify an alarm trigger with a "DURATION" value type. The
parameter specifies whether the alarm will trigger relative to the
start or end of the calendar component. The parameter value START
will set the alarm to trigger off the start of the calendar
component; the parameter value END will set the alarm to trigger
off the end of the calendar component. If the parameter is not
specified on an allowable property, then the default is START.

Example:

TRIGGER;RELATED=END:PT5M

3.2.15. Relationship Type

Parameter Name: RELTYPE

Purpose: To specify the type of hierarchical relationship associated
with the calendar component specified by the property.

Format Definition: This property parameter is defined by the
following notation:

reltypeparam = "RELTYPE" "="
("PARENT" ; Parent relationship. Default. relationship - Default
/ "CHILD" ; Child relationship
/ "SIBLING" ; Sibling relationship
/ iana-token ; Some other IANA registered IANA-registered
; iCalendar relationship type
/ x-name) ; A non-standard, experimental
; relationship type

Description: This parameter can be specified on a property that
references another related calendar. The parameter specifies the
hierarchical relationship type of the calendar component
referenced by the property. The parameter value can be PARENT, to
indicate that the referenced calendar component is a superior of
calendar component; CHILD to indicate that the referenced calendar
component is a subordinate of the calendar component; or SIBLING
to indicate that the referenced calendar component is a peer of
the calendar component. If this parameter is not specified on an
allowable property, the default relationship type is PARENT.
Applications MUST treat x-name and iana-token value values they don't
recognized
recognize the same way as they would the PARENT value.

Example:

RELATED-TO;RELTYPE=SIBLING:19960401-080045-4000F192713@
example.com

3.2.16. Participation Role

Parameter Name: ROLE

Purpose: To specify the participation role for the calendar user
specified by the property.

Format Definition: This property parameter is defined by the
following notation:

roleparam = "ROLE" "="
("CHAIR" ; Indicates chair of the
; calendar entity
/ "REQ-PARTICIPANT" ; Indicates a participant whose
; participation is required
/ "OPT-PARTICIPANT" ; Indicates a participant whose
; participation is optional
/ "NON-PARTICIPANT" ; Indicates a participant who
; is copied for information
; purposes only
/ x-name ; Experimental role
/ iana-token) ; Other IANA role
; Default is REQ-PARTICIPANT

Description: This parameter can be specified on properties with a
CAL-ADDRESS value type. The parameter specifies the participation
role for the calendar user specified by the property in the group
schedule calendar component. If not specified on a property that
allows this parameter, the default value is REQ-PARTICIPANT.
Applications MUST treat x-name and iana-token value values they don't
recognized
recognize the same way as they would the REQ-PARTICIPANT value.

Example:

ATTENDEE;ROLE=CHAIR:mailto:mrbig@example.com

3.2.17. RSVP Expectation

Parameter Name: RSVP

Purpose: To specify whether there is an expectation of a favor of a
reply from the calendar user specified by the property value.

Format Definition: This property parameter is defined by the
following notation:

rsvpparam = "RSVP" "=" ("TRUE" / "FALSE")
; Default is FALSE
Description: This parameter can be specified on properties with a
CAL-ADDRESS value type. The parameter identifies the expectation
of a reply from the calendar user specified by the property value.
This parameter is used by the "Organizer" to request a
participation status reply from an "Attendee" of a group scheduled group-scheduled
event or to-do. If not specified on a property that allows this
parameter, the default value is FALSE.

Example:

ATTENDEE;RSVP=TRUE:mailto:jsmith@example.com

3.2.18. Sent By

Parameter Name: SENT-BY

Purpose: To specify the calendar user that is acting on behalf of
the calendar user specified by the property.

Format Definition: This property parameter is defined by the
following notation:

sentbyparam = "SENT-BY" "=" DQUOTE cal-address DQUOTE

Description: This parameter can be specified on properties with a
CAL-ADDRESS value type. The parameter specifies the calendar user
that is acting on behalf of the calendar user specified by the
property. The parameter value MUST be a mailto URI as defined in
[RFC2368]. The individual calendar address parameter values MUST
each be specified in a quoted-string.

Example:

ORGANIZER;SENT-BY="mailto:sray@example.com":mailto:
jsmith@example.com

3.2.19. Time Zone Identifier

Parameter Name: TZID

Purpose: To specify the identifier for the time zone definition for
a time component in the property value.

Format Definition: This property parameter is defined by the
following notation:

tzidparam = "TZID" "=" [tzidprefix] paramtext
tzidprefix = "/"

Description: This parameter MUST be specified on the "DTSTART",
"DTEND", "DUE", "EXDATE" "EXDATE", and "RDATE" properties when either a
DATE-TIME or TIME value type is specified and when the value is
not either
neither a UTC or a "floating" time. Refer to the DATE-TIME or
TIME value type definition for a description of UTC and "floating
time" formats. This property parameter specifies a text value
which
that uniquely identifies the "VTIMEZONE" calendar component to be
used when evaluating the time portion of the property. The value
of the "TZID" property parameter will be equal to the value of the
"TZID" property for the matching time zone definition. An
individual "VTIMEZONE" calendar component MUST be specified for
each unique "TZID" parameter value specified in the iCalendar
object.

The parameter MUST be specified on properties with a DATE-TIME
value if the DATE-TIME is not either a UTC or a "floating" time.
Failure to include and follow VTIMEZONE definitions in iCalendar
objects may lead to inconsistent understanding of the local time
at any given location.

The presence of the SOLIDUS character (US-ASCII decimal 47) as a prefix, indicates that
this "TZID" represents a unique ID in a globally defined time zone
registry (when such registry is defined).

Note: This document does not define a naming convention for
time zone identifiers. Implementers may want to use the naming
conventions defined in existing time zone specifications such
as the public-domain TZ database [TZDB]. The specification of
globally unique time zone identifiers is not addressed by this
document and is left for future study.

The following are examples of this property parameter:

DTSTART;TZID=America/New_York:19980119T020000

DTEND;TZID=America/New_York:19980119T030000

The "TZID" property parameter MUST NOT be applied to DATE
properties,
properties and DATE-TIME or TIME properties whose time values are
specified in UTC.

The use of local time in a DATE-TIME or TIME value without the
"TZID" property parameter is to be interpreted as floating time,
regardless of the existence of "VTIMEZONE" calendar components in
the iCalendar object.

For more information information, see the sections on the value types DATE-TIME DATE-
TIME and TIME.

3.2.20. Value Data Types

Parameter Name: VALUE

Purpose: To explicitly specify the value type format for a property
value.

Format Definition: This property parameter is defined by the
following notation:

valuetypeparam = "VALUE" "=" valuetype

valuetype = ("BINARY"
/ "BOOLEAN"
/ "CAL-ADDRESS"
/ "DATE"
/ "DATE-TIME"
/ "DURATION"
/ "FLOAT"
/ "INTEGER"
/ "PERIOD"
/ "RECUR"
/ "TEXT"
/ "TIME"
/ "URI"
/ "UTC-OFFSET"
/ x-name
; Some experimental iCalendar value type.
/ iana-token)
; Some other IANA registered IANA-registered iCalendar value type.

Description: This parameter specifies the value type and format of
the property value. The property values MUST be of a single value
type. For example, a "RDATE" property cannot have a combination
of DATE-TIME and TIME value types.

If the property's value is the default value type, then this
parameter need not be specified. However, if the property's
default value type is overridden by some other allowable value
type, then this parameter MUST be specified.

Applications MUST preserve the value data for x-name and iana-
token values that they don't recognize without attempting to
interpret or parse the value data.

3.3. Property Value Data Types

The properties in an iCalendar object are strongly typed. The
definition of each property restricts the value to be one of the
value data types, or simply value types, defined in this section.
The value type for a property will either be specified implicitly as
the default value type or will be explicitly specified with the
"VALUE" parameter. If the value type of a property is one of the
alternate valid types, then it MUST be explicitly specified with the
"VALUE" parameter.

3.3.1. Binary

Value Name: BINARY

Purpose: This value type is used to identify properties that contain
a character encoding of inline binary data. For example, an
inline attachment of a document might be included in an iCalendar
object.

Format Definition: This value type is defined by the following
notation:

binary = *(4b-char) [b-end]
; A "BASE64" encoded character string, as defined by [RFC4648].

b-end = (2b-char "==") / (3b-char "=")

b-char = ALPHA / DIGIT / "+" / "/"

Description: Property values with this value type MUST also include
the inline encoding parameter sequence of ";ENCODING=BASE64".
That is, all inline binary data MUST first be character encoded
using the "BASE64" encoding method defined in [RFC2045]. No
additional content value encoding (i.e., BACKSLASH character
encoding, see Section 3.3.11) is defined for this value type.

Example: The following is an example of a "BASE64" encoded binary
value data. data:

ATTACH;FMTTYPE=image/vnd.microsoft.icon;ENCODING=BASE64;VALUE
=BINARY:AAABAAEAEBAQAAEABAAoAQAAFgAAACgAAAAQAAAAIAAAAAEABAAA
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAACAAAAAgIAAAICAgADAwMAA////AAAA
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAAAAAAAAAAAAAAAAAAAAAMwAAAAAAABNEMQAAAAAAAkQgAAAAAAJEREQgAA
ACECQ0QgEgAAQxQzM0E0AABERCRCREQAADRDJEJEQwAAAhA0QwEQAAAAAERE
AAAAAAAAREQAAAAAAAAkQgAAAAAAAAMgAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAAAAAAAAAAA

3.3.2. Boolean

Value Name: BOOLEAN

Purpose: This value type is used to identify properties that contain
either a "TRUE" or "FALSE" Boolean value.

Format Definition: This value type is defined by the following
notation:

boolean = "TRUE" / "FALSE"

Description: These values are case insensitive case-insensitive text. No additional
content value encoding (i.e., BACKSLASH character encoding, see
Section 3.3.11) is defined for this value type.

Example: The following is an example of a hypothetical property that
has a BOOLEAN value type:

TRUE

3.3.3. Calendar User Address

Value Name: CAL-ADDRESS

Purpose: This value type is used to identify properties that contain
a calendar user address.

Format Definition: This value type is defined by the following
notation:

cal-address = uri

Description: The value is a URI as defined by [RFC3986] or any other
IANA registered
IANA-registered form for a URI. When used to address an Internet
email transport address for a calendar user, the value MUST be a
mailto URI, as defined by [RFC2368]. No additional content value
encoding (i.e., BACKSLASH character encoding, see Section 3.3.11)
is defined for this value type.

Example:

mailto:jane_doe@example.com

3.3.4. Date

Value Name: DATE

Purpose: This value type is used to identify values that contain a
calendar date.

Format Definition: This value type is defined by the following
notation:

date = date-value

date-value = date-fullyear date-month date-mday
date-fullyear = 4DIGIT
date-month = 2DIGIT ;01-12
date-mday = 2DIGIT ;01-28, 01-29, 01-30, 01-31
;based on month/year

Description: If the property permits, multiple "date" values are
specified as a COMMA character (US-ASCII decimal 44) separated COMMA-separated list of values. The format for the
value type is based on the [ISO.8601.2004] complete
representation, basic format for a calendar date. The textual
format specifies a four-digit year, two-digit month, and two-digit
day of the month. There are no separator characters between the
year, month month, and day component text.

No additional content value encoding (i.e., BACKSLASH character
encoding, see Section 3.3.11) is defined for this value type.

Example: The following represents July 14, 1997:

19970714

3.3.5. Date-Time

Value Name: DATE-TIME

Purpose: This value type is used to identify values that specify a
precise calendar date and time of day.

Format Definition: This value type is defined by the following
notation:

date-time = date "T" time ;As specified in the date DATE and time TIME
;value definitions
Description: If the property permits, multiple "date-time" "DATE-TIME" values
are specified as a COMMA character (US-ASCII decimal 44) separated COMMA-separated list of values. No additional
content value encoding (i.e., BACKSLASH character encoding, see
Section 3.3.11) is defined for this value type.

The "DATE-TIME" value type is used to identify values that contain
a precise calendar date and time of day. The format is based on
the [ISO.8601.2004] complete representation, basic format for a
calendar date and time of day. The text format is a concatenation
of the "date", followed by the LATIN CAPITAL LETTER T character
(US-ASCII decimal 84) character,
the time designator, followed by the "time" format.

The "DATE-TIME" value type expresses time values in three forms:

The form of date and time with UTC offset MUST NOT be used. For
example, the following is not valid for a date-time DATE-TIME value:

19980119T230000-0800 ;Invalid time format

FORM #1: DATE WITH LOCAL TIME

The date with local time form is simply a DATE-TIME value that
does not contain the UTC designator nor does it reference a time
zone. For example, the following represents January 18, 1998, at
11 PM:

19980118T230000

DATE-TIME values of this type are said to be "floating" and are
not bound to any time zone in particular. They are used to
represent the same hour, minute, and second value regardless of
which time zone is currently being observed. For example, an
event can be defined that indicates that an individual will be
busy from 11:00 AM to 1:00 PM every day, no matter which time zone
the person is in. In these cases, a local time can be specified.
The recipient of an iCalendar object with a property value
consisting of a local time, without any relative time zone
information, SHOULD interpret the value as being fixed to whatever
time zone the "ATTENDEE" is in at any given moment. This means
that two "Attendees", in different time zones, receiving the same
event definition as a floating time, may be participating in the
event at different actual times. Floating time SHOULD only be
used where that is the reasonable behavior.

In most cases, a fixed time is desired. To properly communicate a
fixed time in a property value, either UTC time or local time with
time zone reference MUST be specified.

The use of local time in a DATE-TIME value without the "TZID"
property parameter is to be interpreted as floating time,
regardless of the existence of "VTIMEZONE" calendar components in
the iCalendar object.

FORM #2: DATE WITH UTC TIME

The date with UTC time, or absolute time, is identified by a LATIN
CAPITAL LETTER Z suffix character (US-ASCII decimal 90), character, the UTC designator, appended to
the time value. For example, the following represents January 19,
1998, at 0700 UTC:

19980119T070000Z

The "TZID" property parameter MUST NOT be applied to DATE-TIME
properties whose time values are specified in UTC.

FORM #3: DATE WITH LOCAL TIME AND TIME ZONE REFERENCE

The date and local time with reference to time zone information is
identified by the use the "TZID" property parameter to reference
the appropriate time zone definition. "TZID" is discussed in
detail in Section 3.2.19. For example, the following represents
2:00 A.M. in New York on Janurary January 19, 1998:

TZID=America/New_York:19980119T020000

If, based on the definition of the referenced time zone, the local
time described occurs more than once (when changing from daylight
to standard time), the DATE-TIME value refers to the first
occurence
occurrence of the referenced time. Thus, TZID=America/
New_York:20071104T013000 indicates November 4, 2007 at 1:30 A.M.
EDT (UTC-04:00). If the local time described does not occur (when
changing from standard to daylight time), the DATE-TIME value is
interpreted using the UTC offset before the gap in local times.
Thus, TZID=America/New_York:20070311T023000 indicates March 11,
2007 at 3:30 A.M. EDT (UTC-04:00), one hour after 1:30 A.M. EST
(UTC-05:00).

A time value MUST only specify the second 60 when specifying a
positive leap second. For example:

19970630T235960Z

Implementations which that do not support leap seconds SHOULD interpret
the second 60 as equivalent to the second 59.

Example: The following represents July 14, 1997, at 1:30 PM in New
York City in each of the three time formats, using the "DTSTART"
property.

DTSTART:19970714T133000 ; Local time
DTSTART:19970714T173000Z ; UTC time
DTSTART;TZID=America/New_York:19970714T133000
; Local time and time
; zone reference

3.3.6. Duration

Value Name: DURATION

Purpose: This value type is used to identify properties that contain
a duration of time.

Format Definition: This value type is defined by the following
notation:

dur-value = (["+"] / "-") "P" (dur-date / dur-time / dur-week)

dur-date = dur-day [dur-time]
dur-time = "T" (dur-hour / dur-minute / dur-second)
dur-week = 1*DIGIT "W"
dur-hour = 1*DIGIT "H" [dur-minute]
dur-minute = 1*DIGIT "M" [dur-second]
dur-second = 1*DIGIT "S"
dur-day = 1*DIGIT "D"

Description: If the property permits, multiple "duration" values are
specified by a COMMA character (US-ASCII decimal 44) separated COMMA-separated list of values. The format is
based on the [ISO.8601.2004] complete representation basic format
with designators for the duration of time. The format can
represent nominal durations (weeks and days) and accurate
durations (hours, minutes, and seconds). Note that unlike [ISO.8601.2004]
[ISO.8601.2004], this value type doesn't support the "Y" and "M"
designators to specify durations in terms of years and months.

The duration of a week or a day depends on its position in the
calendar. In the case of discontinuities in the time scale, such
as the change from standard time to daylight time and back, the
computation of the exact duration requires the substraction subtraction or
addition of the change of duration of the discontinuity. Leap
seconds MUST NOT be considered when computing an exact duration.
When computing an exact duration, the greatest order time
components MUST be added first, that is, the number of days MUST
be added first, followed by the number of hours, number of
minutes, and number of seconds.

Negative durations are typically used to schedule an alarm to
trigger before an associated time (see Section 3.8.6.3).

No additional content value encoding (i.e., BACKSLASH character
encoding, see Section 3.3.11) are defined for this value type.

Example: A duration of 15 days, 5 hours hours, and 20 seconds would be:

P15DT5H0M20S

A duration of 7 weeks would be:

P7W

3.3.7. Float

Value Name: FLOAT

Purpose: This value type is used to identify properties that contain
a real number real-number value.

Format Definition: This value type is defined by the following
notation:

float = (["+"] / "-") 1*DIGIT ["." 1*DIGIT]

Description: If the property permits, multiple "float" values are
specified by a COMMA character (US-ASCII decimal 44) separated COMMA-separated list of values.

No additional content value encoding (i.e., BACKSLASH character
encoding, see Section 3.3.11) is defined for this value type.

Example:

1000000.0000001
1.333
-3.14

3.3.8. Integer

Value Name: INTEGER

Purpose: This value type is used to identify properties that contain
a signed integer value.

Format Definition: This value type is defined by the following
notation:

integer = (["+"] / "-") 1*DIGIT

Description: If the property permits, multiple "integer" values are
specified by a COMMA character (US-ASCII decimal 44) separated COMMA-separated list of values. The valid range
for "integer" is -2147483648 to 2147483647. If the sign is not
specified, then the value is assumed to be positive.

No additional content value encoding (i.e., BACKSLASH character
encoding, see Section 3.3.11) is defined for this value type.

Example:

1234567890
-1234567890
+1234567890
432109876

3.3.9. Period of Time

Value Name: PERIOD

Purpose: This value type is used to identify values that contain a
precise period of time.

Format Definition: This value type is defined by the following
notation:

period = period-explicit / period-start

period-explicit = date-time "/" date-time
; [ISO.8601.2004] complete representation basic format for a
; period of time consisting of a start and end. The start MUST
; be before the end.

period-start = date-time "/" dur-value
; [ISO.8601.2004] complete representation basic format for a
; period of time consisting of a start and positive duration
; of time.

Description: If the property permits, multiple "period" values are
specified by a COMMA character (US-ASCII decimal 44) separated COMMA-separated list of values. There are two
forms of a period of time. First, a period of time is identified
by its start and its end. This format is based on the
[ISO.8601.2004] complete representation, basic format for "DATE-TIME" "DATE-
TIME" start of the period, followed by a SOLIDUS character (US-ASCII decimal 47),
followed by the "DATE-
TIME" "DATE-TIME" of the end of the period. The start
of the period MUST be before the end of the period. Second, a
period of time can also be defined by a start and a positive
duration of time. The format is based on the [ISO.8601.2004]
complete representation, basic format for the "DATE-TIME" start of
the period, followed by a SOLIDUS character (US-ASCII decimal 47), character, followed by the
[ISO.8601.2004] basic format for "DURATION" of the period.

Example: The period starting at 18:00:00 UTC, on January 1, 1997 and
ending at 07:00:00 UTC on January 2, 1997 would be:

19970101T180000Z/19970102T070000Z

The period start at 18:00:00 on January 1, 1997 and lasting 5
hours and 30 minutes would be:

19970101T180000Z/PT5H30M

No additional content value encoding (i.e., BACKSLASH character
encoding, see Section 3.3.11) is defined for this value type.

3.3.10. Recurrence Rule

Value Name: RECUR

Purpose: This value type is used to identify properties that contain
a recurrence rule specification.

Format Definition: This value type is defined by the following
notation:

recur = recur-rule-part *( ";" recur-rule-part )
;
; The rule parts are not ordered in any
; particular sequence sequence.
;
; The FREQ rule part is REQUIRED,
; but MUST NOT occur more than once once.
;
; The UNTIL or COUNT rule parts are OPTIONAL,
; but they MUST NOT occur in the same 'recur' 'recur'.
;
; The other rule parts are OPTIONAL,
; but MUST NOT occur more than once once.

recur-rule-part = ( "FREQ" "=" freq )
/ ( "UNTIL" "=" enddate )
/ ( "COUNT" "=" 1*DIGIT )
/ ( "INTERVAL" "=" 1*DIGIT )
/ ( "BYSECOND" "=" byseclist )
/ ( "BYMINUTE" "=" byminlist )
/ ( "BYHOUR" "=" byhrlist )
/ ( "BYDAY" "=" bywdaylist )
/ ( "BYMONTHDAY" "=" bymodaylist )
/ ( "BYYEARDAY" "=" byyrdaylist )
/ ( "BYWEEKNO" "=" bywknolist )
/ ( "BYMONTH" "=" bymolist )
/ ( "BYSETPOS" "=" bysplist )
/ ( "WKST" "=" weekday )

freq = "SECONDLY" / "MINUTELY" / "HOURLY" / "DAILY"
/ "WEEKLY" / "MONTHLY" / "YEARLY"

enddate = date / date-time

byseclist = ( seconds *("," seconds) )

seconds = 1*2DIGIT ;0 to 60

byminlist = ( minutes *("," minutes) )

minutes = 1*2DIGIT ;0 to 59

byhrlist = ( hour *("," hour) )

hour = 1*2DIGIT ;0 to 23

bywdaylist = ( weekdaynum *("," weekdaynum) )

weekdaynum = [[plus / minus] ordwk] weekday

plus = "+"

minus = "-"

ordwk = 1*2DIGIT ;1 to 53

weekday = "SU" / "MO" / "TU" / "WE" / "TH" / "FR" / "SA"
;Corresponding to SUNDAY, MONDAY, TUESDAY, WEDNESDAY, THURSDAY,
;FRIDAY, and SATURDAY days of the week.

bymodaylist = ( monthdaynum *("," monthdaynum) )

monthdaynum = [plus / minus] ordmoday

ordmoday = 1*2DIGIT ;1 to 31
byyrdaylist = ( yeardaynum *("," yeardaynum) )

yeardaynum = [plus / minus] ordyrday

ordyrday = 1*3DIGIT ;1 to 366

bywknolist = ( weeknum *("," weeknum) )

weeknum = [plus / minus] ordwk

bymolist = ( monthnum *("," monthnum) )

monthnum = 1*2DIGIT ;1 to 12

bysplist = ( setposday *("," setposday) )

setposday = yeardaynum

Description: This value type is a structured value consisting of a
list of one or more recurrence grammar parts. Each rule part is
defined by a NAME=VALUE pair. The rule parts are separated from
each other by the SEMICOLON character (US-ASCII decimal 59). character. The rule parts are not
ordered in any particular sequence. Individual rule parts MUST
only be specified once. Compliant applications MUST accept rule
parts ordered in any sequence, but to ensure backward
compatibility with applications that pre-date this revision of
iCalendar the FREQ rule part MUST be the first rule part specified
in a RECUR value.

The FREQ rule part identifies the type of recurrence rule. This
rule part MUST be specified in the recurrence rule. Valid values
include SECONDLY, to specify repeating events based on an interval
of a second or more; MINUTELY, to specify repeating events based
on an interval of a minute or more; HOURLY, to specify repeating
events based on an interval of an hour or more; DAILY, to specify
repeating events based on an interval of a day or more; WEEKLY, to
specify repeating events based on an interval of a week or more;
MONTHLY, to specify repeating events based on an interval of a
month or more; and YEARLY, to specify repeating events based on an
interval of a year or more.

The INTERVAL rule part contains a positive integer representing at
which intervals the recurrence rule repeats. The default value is
"1", meaning every second for a SECONDLY rule, every minute for a
MINUTELY rule, every hour for an HOURLY rule, every day for a
DAILY rule, every week for a WEEKLY rule, every month for a
MONTHLY rule, and every year for a YEARLY rule. For example,
within a DAILY rule, a value of "8" means every eight days.

The UNTIL rule part defines a DATE or DATE-TIME value which that bounds
the recurrence rule in an inclusive manner. If the value
specified by UNTIL is synchronized with the specified recurrence,
this DATE or DATE-TIME becomes the last instance of the
recurrence. The value of the UNTIL rule part MUST have the same
value type as the "DTSTART" property. Furthermore, if the
"DTSTART" property is specified as a date with local time, then
the UNTIL rule part MUST also be specified as a date with local
time. If the "DTSTART" property is specified as a date with UTC
time or a date with local time and time zone reference, then the
UNTIL rule part MUST be specified as a date with UTC time. In the
case of the "STANDARD" and "DAYLIGHT" sub-components the UNTIL
rule part MUST always be specified as a date with UTC time. If
specified as a DATE-TIME value, then it MUST be specified in a UTC
time format. If not present, and the COUNT rule part is also not
present, the "RRULE" is considered to repeat forever.

The COUNT rule part defines the number of occurrences at which to
range-bound the recurrence. The "DTSTART" property value always
counts as the first occurrence.

The BYSECOND rule part specifies a COMMA character (US-ASCII
decimal 44) separated COMMA-separated list of seconds
within a minute. Valid values are 0 to 60. The BYMINUTE rule
part specifies a COMMA
character (US-ASCII decimal 44) separated COMMA-separated list of minutes within an hour.
Valid values are 0 to 59. The BYHOUR rule part specifies a COMMA character (US-ASCII decimal 44) COMMA-
separated list of hours of the day. Valid values are 0 to 23.
The BYSECOND, BYMINUTE and BYHOUR rule parts MUST NOT be specified
when the associated "DTSTART" property has a DATE value type.
These rule parts MUST be ignored in RECUR value that violate the
above requirement (e.g., generated by applications that pre-date
this revision of iCalendar).

The BYDAY rule part specifies a COMMA character (US-ASCII decimal
44) separated COMMA-separated list of days of
the week; SU indicates Sunday; MO indicates Monday; TU indicates
Tuesday; WE indicates Wednesday; TH indicates Thursday; FR
indicates Friday; and SA indicates Saturday.

Each BYDAY value can also be preceded by a positive (+n) or
negative (-n) integer. If present, this indicates the nth
occurrence of a specific day within the MONTHLY or YEARLY "RRULE".
For example, within a MONTHLY rule, +1MO (or simply 1MO)
represents the first Monday within the month, whereas -1MO
represents the last Monday of the month. The numeric value in a
BYDAY rule part with the FREQ rule part set to YEARLY corresponds
to an offset within the month when the BYMONTH rule part is
present, and corresponds to an offset within the year when the
BYWEEKNO or BYMONTH rule parts are present. If an integer
modifier is not present, it means all days of this type within the
specified frequency. For example, within a MONTHLY rule, MO
represents all Mondays within the month. The BYDAY rule part MUST
NOT be specified with a numeric value when the FREQ rule part is
not set to MONTHLY or YEARLY. Furthermore, the BYDAY rule part
MUST NOT be specified with a numeric value with the FREQ rule part
set to YEARLY when the BYWEEKNO rule part is specified.

The BYMONTHDAY rule part specifies a COMMA character (US-ASCII
decimal 44) separated COMMA-separated list of days
of the month. Valid values are 1 to 31 or -31 to -1. For
example, -10 represents the tenth to the last day of the month.
The BYMONTHDAY rule part MUST NOT be specified when the FREQ rule
part is set to WEEKLY.

The BYYEARDAY rule part specifies a COMMA character (US-ASCII
decimal 44) separated COMMA-separated list of days
of the year. Valid values are 1 to 366 or -366 to -1. For
example, -1 represents the last day of the year (December 31st)
and -306 represents the 306th to the last day of the year (March
1st). The BYYEARDAY rule part MUST NOT be specified when the FREQ
rule part is set to DAILY, WEEKLY, or MONTHLY.

The BYWEEKNO rule part specifies a COMMA character (US-ASCII
decimal 44) separated COMMA-separated list of
ordinals specifying weeks of the year. Valid values are 1 to 53
or -53 to -1. This corresponds to weeks according to week
numbering as defined in [ISO.8601.2004]. A week is defined as a
seven day period, starting on the day of the week defined to be
the week start (see WKST). Week number one of the calendar year
is the first week which that contains at least four (4) days in that
calendar year. This rule part MUST NOT be used when the FREQ rule
part is set to anything other than YEARLY. For example, 3
represents the third week of the year.

Note: Assuming a Monday week start, week 53 can only occur when
Thursday is January 1 or if it is a leap year and Wednesday is
January 1.

The BYMONTH rule part specifies a COMMA character (US-ASCII
decimal 44) separated COMMA-separated list of months
of the year. Valid values are 1 to 12.

The WKST rule part specifies the day on which the workweek starts.
Valid values are MO, TU, WE, TH, FR, SA SA, and SU. This is
significant when a WEEKLY "RRULE" has an interval greater than 1,
and a BYDAY rule part is specified. This is also significant when
in a YEARLY "RRULE" when a BYWEEKNO rule part is specified. The
default value is MO.

The BYSETPOS rule part specifies a COMMA character (US-ASCII
decimal 44) separated COMMA-separated list of values which
that corresponds to the nth occurrence within the set of
recurrence instances specified by the rule. BYSETPOS operates on
a set of recurrence instances in one interval of the recurrence
rule. For example, in a WEEKLY rule, the interval would be one
week A set of recurrence instances starts at the beginning of the
interval defined by the FREQ rule part. Valid values are 1 to 366
or -366 to -1. It MUST only be used in conjunction with another
BYxxx rule part. For example "the last work day of the month"
could be represented as:

FREQ=MONTHLY;BYDAY=MO,TU,WE,TH,FR;BYSETPOS=-1

Each BYSETPOS value can include a positive (+n) or negative (-n)
integer. If present, this indicates the nth occurrence of the
specific occurrence within the set of occurences occurrences specified by the
rule.

Recurrence rules may generate recurrence instances with an invalid
date (e.g., February 30) or nonexistent local time (e.g., 1:30 AM
on a day where the local time is moved forward by an hour at 1:00
AM). Such recurrence instances MUST be ignored and MUST NOT be
counted as part of the recurrence set.

Information, not contained in the rule, necessary to determine the
various recurrence instance start time and dates are derived from
the Start Time ("DTSTART") component attribute. For example,
"FREQ=YEARLY;BYMONTH=1" doesn't specify a specific day within the
month or a time. This information would be the same as what is
specified for "DTSTART".

BYxxx rule parts modify the recurrence in some manner. BYxxx rule
parts for a period of time which that is the same or greater than the
frequency generally reduce or limit the number of occurrences of
the recurrence generated. For example, "FREQ=DAILY;BYMONTH=1"
reduces the number of recurrence instances from all days (if
BYMONTH rule part is not present) to all days in January. BYxxx
rule parts for a period of time less than the frequency generally
increase or expand the number of occurrences of the recurrence.
For example, "FREQ=YEARLY;BYMONTH=1,2" increases the number of
days within the yearly recurrence set from 1 (if BYMONTH rule part
is not present) to 2.

If multiple BYxxx rule parts are specified, then after evaluating
the specified FREQ and INTERVAL rule parts, the BYxxx rule parts
are applied to the current set of evaluated occurrences in the
following order: BYMONTH, BYWEEKNO, BYYEARDAY, BYMONTHDAY, BYDAY,
BYHOUR, BYMINUTE, BYSECOND and BYSETPOS; then COUNT and UNTIL are
evaluated.

The table below summarizes the dependency of BYxxx rule part
expand or limit behaviour behavior on the FREQ rule part value.

The term "N/A" means that the corresponding BYxxx rule part MUST
NOT be used with the corresponding FREQ value.

BYDAY has some special behaviour behavior depending on the FREQ value and
this is described in separate notes below the table.

Note 1: Limit if BYMONTHDAY is present, otherwise present; otherwise, special expand
for MONTHLY.

Note 2: Limit if BYYEARDAY or BYMONTHDAY is present, otherwise present; otherwise,
special expand for WEEKLY if BYWEEKNO present, otherwise present; otherwise,
special expand for MONTHLY if BYMONTH present, otherwise present; otherwise,
special expand for YEARLY.

Here is an example of evaluating multiple BYxxx rule parts.

DTSTART;TZID=America/New_York:19970105T083000
RRULE:FREQ=YEARLY;INTERVAL=2;BYMONTH=1;BYDAY=SU;BYHOUR=8,9;
BYMINUTE=30
First, the "INTERVAL=2" would be applied to "FREQ=YEARLY" to
arrive at "every other year". Then, "BYMONTH=1" would be applied
to arrive at "every January, every other year". Then, "BYDAY=SU"
would be applied to arrive at "every Sunday in January, every
other year". Then, "BYHOUR=8,9" would be applied to arrive at
"every Sunday in January at 8 AM and 9 AM, every other year".
Then, "BYMINUTE=30" would be applied to arrive at "every Sunday in
January at 8:30 AM and 9:30 AM, every other year". Then, lacking
information from "RRULE", the second is derived from "DTSTART", to
end up in "every Sunday in January at 8:30:00 AM and 9:30:00 AM,
every other year". Similarly, if the BYMINUTE, BYHOUR, BYDAY,
BYMONTHDAY
BYMONTHDAY, or BYMONTH rule part were missing, the appropriate
minute, hour, day day, or month would have been retrieved from the
"DTSTART" property.

If the computed local start time of a recurrence instance does not
exist, or occurs more than once, for the specified time zone, the
time of the recurrence instance is interpreted in the same manner
as an explicit DATE-TIME value describing that date and time, as
specified in Section 3.3.5.

No additional content value encoding (i.e., BACKSLASH character
encoding, see Section 3.3.11) is defined for this value type.

Example: The following is a rule which that specifies 10 occurences which occurrences that
occur every other day:

FREQ=DAILY;COUNT=10;INTERVAL=2

There are other examples specified in Section 3.8.5.3.

3.3.11. Text

Value Name: TEXT

Purpose: This value type is used to identify values that contain
human readable
human-readable text.

Format Definition: This value type is defined by the following
notation.
notation:

text = *(TSAFE-CHAR / ":" / DQUOTE / ESCAPED-CHAR)
; Folded according to description above

ESCAPED-CHAR = ("\\" / "\;" / "\," / "\N" / "\n")
; \\ encodes \, \N or \n encodes newline
; \; encodes ;, \, encodes ,

TSAFE-CHAR = WSP / %x21 / %x23-2B / %x2D-39 / %x3C-5B /
%x5D-7E / NON-US-ASCII
; Any character except CONTROLs not needed by the current
; character set, DQUOTE, ";", ":", "\", ","

Description: If the property permits, multiple TEXT values are
specified by a COMMA character (US-ASCII decimal 44) separated COMMA-separated list of values.

The language in which the text is represented can be controlled by
the "LANGUAGE" property parameter.

An intentional formatted text line break MUST only be included in
a "TEXT" property value by representing the line break with the
character sequence of BACKSLASH (US-ASCII decimal 92), BACKSLASH, followed by a LATIN SMALL LETTER
N (US-ASCII decimal 110) or a LATIN CAPITAL LETTER N (US-ASCII decimal 78), N, that is "\n" or "\N".

The "TEXT" property values may also contain special characters
that are used to signify delimiters, such as a COMMA character for
lists of values or a SEMICOLON character for structured values.
In order to support the inclusion of these special characters in
"TEXT" property values, they MUST be escaped with a BACKSLASH
character. A BACKSLASH character (US-ASCII decimal 92) in a "TEXT" property value MUST
be escaped with another BACKSLASH character. A COMMA character in
a "TEXT" property value MUST be escaped with a BACKSLASH character (US-ASCII decimal 92).
character. A SEMICOLON character in a "TEXT" property value MUST
be escaped with a BACKSLASH character (US-ASCII decimal 92). character. However, a COLON character
in a "TEXT" property value SHALL NOT be escaped with a BACKSLASH
character.

Example: A multiple line value of:

Project XYZ Final Review
Conference Room - 3B
Come Prepared.

would be represented as:

Project XYZ Final Review\nConference Room - 3B\nCome Prepared.

3.3.12. Time

Value Name: TIME

Purpose: This value type is used to identify values that contain a
time of day.

Format Definition: This value type is defined by the following
notation:

time = time-hour time-minute time-second [time-utc]

time-hour = 2DIGIT ;00-23
time-minute = 2DIGIT ;00-59
time-second = 2DIGIT ;00-60
;The "60" value is used to account for positive "leap" seconds.

time-utc = "Z"

Description: If the property permits, multiple "time" values are
specified by a COMMA character (US-ASCII decimal 44) separated COMMA-separated list of values. No additional
content value encoding (i.e., BACKSLASH character encoding, see
Section 3.3.11) is defined for this value type.

The "TIME" value type is used to identify values that contain a
time of day. The format is based on the [ISO.8601.2004] complete
representation, basic format for a time of day. The text format
consists of a two-digit two-digit, 24-hour of the day (i.e., values 00-23),
two-digit minute in the hour (i.e., values 00-59), and two-digit
seconds in the minute (i.e., values 00-60). The seconds value of
60 MUST only be used to account for positive "leap" seconds.
Fractions of a second are not supported by this format.

In parallel to the "DATE-TIME" definition above, the "TIME" value
type expresses time values in three forms:

The form of time with UTC offset MUST NOT be used. For example,
the following is not valid for a time value:

230000-0800 ;Invalid time format

FORM #1 LOCAL TIME

The local time form is simply a time value that does not contain
the UTC designator nor does it reference a time zone. For
example, 11:00 PM:

230000
Time values of this type are said to be "floating" and are not
bound to any time zone in particular. They are used to represent
the same hour, minute, and second value regardless of which time
zone is currently being observed. For example, an event can be
defined that indicates that an individual will be busy from 11:00
AM to 1:00 PM every day, no matter which time zone the person is
in. In these cases, a local time can be specified. The recipient
of an iCalendar object with a property value consisting of a local
time, without any relative time zone information, SHOULD interpret
the value as being fixed to whatever time zone the "ATTENDEE" is
in at any given moment. This means that two "Attendees", may
participate in the same event at different UTC times; floating
time SHOULD only be used where that is reasonable behavior.

In most cases, a fixed time is desired. To properly communicate a
fixed time in a property value, either UTC time or local time with
time zone reference MUST be specified.

The use of local time in a TIME value without the "TZID" property
parameter is to be interpreted as floating time, regardless of the
existence of "VTIMEZONE" calendar components in the iCalendar
object.

FORM #2: UTC TIME

UTC time, or absolute time, is identified by a LATIN CAPITAL
LETTER Z suffix character (US-ASCII decimal 90), character, the UTC designator, appended to the
time value. For example, the following represents 07:00 AM UTC:

070000Z

The "TZID" property parameter MUST NOT be applied to TIME
properties whose time values are specified in UTC.

FORM #3: LOCAL TIME AND TIME ZONE REFERENCE

The local time with reference to time zone information form is
identified by the use the "TZID" property parameter to reference
the appropriate time zone definition. "TZID" is discussed in
detail in Section 3.2.19.

Example: The following represents 8:30 AM in New York in Winter, winter,
five hours behind UTC, in each of the three formats:

083000
133000Z
TZID=America/New_York:083000

3.3.13. URI

Value Name: URI

Purpose: This value type is used to identify values that contain a
uniform resource identifier (URI) type of reference to the
property value.

Format Definition: This value type is defined by the following
notation:

uri = <As defined in section Section 3 of [RFC3986]>

Description: This value type might be used to reference binary
information, for values that are large, or otherwise undesirable
to include directly in the iCalendar object.

Property values with this value type MUST follow the generic URI
syntax defined in [RFC3986].

When a property parameter value is a URI value type, the URI MUST
be specified as a quoted-string value.

No additional content value encoding (i.e., BACKSLASH character
encoding, see Section 3.3.11) is defined for this value type.

Example: The following is a URI for a network file:

http://example.com/my-report.txt

3.3.14. UTC Offset

Value Name: UTC-OFFSET

Purpose: This value type is used to identify properties that contain
an offset from UTC to local time.

Format Definition: This value type is defined by the following
notation:

utc-offset = time-numzone

time-numzone = ("+" / "-") time-hour time-minute [time-second]
Description: The PLUS SIGN (US-ASCII decimal 43) character MUST be specified for positive
UTC offsets (i.e., ahead of UTC). The HYPHEN-MINUS character (US-ASCII decimal 45) MUST
be specified for negative UTC offsets (i.e., behind of UTC). The
value of "-0000" and "-000000" are not allowed. The time-second,
if present, MUST NOT be 60; if absent, it defaults to zero.

No additional content value encoding (i.e., BACKSLASH character
encoding, see Section 3.3.11) is defined for this value type.

Example: The following UTC offsets are given for standard time for
New York (five hours behind UTC) and Geneva (one hour ahead of
UTC):

-0500

+0100

3.4. iCalendar Object

The Calendaring and Scheduling Core Object is a collection of
calendaring and scheduling information. Typically, this information
will consist of an iCalendar stream with a single iCalendar object.
However, multiple iCalendar objects can be sequentially grouped
together in an iCalendar stream. The first line and last line of the
iCalendar object MUST contain a pair of iCalendar object delimiter
strings. The syntax for an iCalendar stream is as follows:

icalstream = 1*icalobject

icalobject = "BEGIN" ":" "VCALENDAR" CRLF
icalbody
"END" ":" "VCALENDAR" CRLF

The following is a simple example of an iCalendar object:

BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//hacksw/handcal//NONSGML v1.0//EN
BEGIN:VEVENT
UID:19970610T172345Z-AF23B2@example.com
DTSTAMP:19970610T172345Z
DTSTART:19970714T170000Z
DTEND:19970715T040000Z
SUMMARY:Bastille Day Party
END:VEVENT
END:VCALENDAR

3.5. Property

A property is the definition of an individual attribute describing a
calendar object or a calendar component. A property takes the form
defined by the "contentline" notation defined in Section 3.1.

The following is an example of a property:

DTSTART:19960415T133000Z

This memo imposes no ordering of properties within an iCalendar
object.

Property names, parameter names names, and enumerated parameter values are
case insensitive.
case-insensitive. For example, the property name "DUE" is the same
as "due" and "Due", DTSTART;TZID=America/New_York:19980714T120000 is
the same as DtStart;TzID=America/New_York:19980714T120000.

3.6. Calendar Components

The body of the iCalendar object consists of a sequence of calendar
properties and one or more calendar components. The calendar
properties are attributes that apply to the calendar object as a
whole. The calendar components are collections of properties that
express a particular calendar semantic. For example, the calendar
component can specify an event, a to-do, a journal entry, time zone
information, free/busy time information, or an alarm.

The body of the iCalendar object is defined by the following
notation:

icalbody = calprops component

calprops = *(
;
; the The following are REQUIRED,
; but MUST NOT occur more than once once.
;
prodid / version /
;
; the The following are OPTIONAL,
; but MUST NOT occur more than once once.
;
calscale / method /
;
; the The following are OPTIONAL,
; and MAY occur more than once once.
;
x-prop / iana-prop
;
)

component = 1*(eventc / todoc / journalc / freebusyc /
timezonec / iana-comp / x-comp)

iana-comp = "BEGIN" ":" iana-token CRLF
1*contentline
"END" ":" iana-token CRLF

x-comp = "BEGIN" ":" x-name CRLF
1*contentline
"END" ":" x-name CRLF

An iCalendar object MUST include the "PRODID" and "VERSION" calendar
properties. In addition, it MUST include at least one calendar
component. Special forms of iCalendar objects are possible to
publish just busy time (i.e., only a "VFREEBUSY" calendar component)
or time zone (i.e., only a "VTIMEZONE" calendar component)
information. In addition, a complex iCalendar object that is used to
capture a complete snapshot of the contents of a calendar is possible
(e.g., composite of many different calendar components). More
commonly, an iCalendar object will consist of just a single "VEVENT",
"VTODO"
"VTODO", or "VJOURNAL" calendar component. Applications MUST ignore
x-comp and iana-comp values they don't recognized. recognize. Applications that
support importing iCalendar objects SHOULD support all of the
component types defined in this document, and SHOULD NOT silently
drop any components as that can lead to user data loss.

3.6.1. Event Component

Component Name: VEVENT

Purpose: Provide a grouping of component properties that describe an
event.

Format Definition: A "VEVENT" calendar component is defined by the
following notation:

eventc = "BEGIN" ":" "VEVENT" CRLF
eventprop *alarmc
"END" ":" "VEVENT" CRLF

eventprop = *(
;
; the The following are REQUIRED,
; but MUST NOT occur more than once once.
;
dtstamp / uid /
;
; the The following is REQUIRED if the component
; appears in an iCalendar object that doesn't
; specify the "METHOD" property, otherwise property; otherwise, it
; is OPTIONAL, OPTIONAL; in any case case, it MUST NOT occur
; more than once once.
;
dtstart /
;
; the The following are OPTIONAL,
; but MUST NOT occur more than once once.
;
class / created / description / geo /
last-mod / location / organizer / priority /
seq / status / summary / transp /
url / recurid /
;
; the The following is OPTIONAL,
; but SHOULD NOT occur more than once once.
;
rrule /
;
; either Either 'dtend' or 'duration' MAY appear in
; a 'eventprop', but 'dtend' and 'duration'
; MUST NOT occur in the same 'eventprop' 'eventprop'.
;
dtend / duration /
;
; the The following are OPTIONAL,
; and MAY occur more than once once.
;
attach / attendee / categories / comment /
contact / exdate / rstatus / related /
resources / rdate / x-prop / iana-prop
;
)
Description: A "VEVENT" calendar component is a grouping of
component properties, and possibly including "VALARM" calendar
components, that represents a scheduled amount of time on a
calendar. For example, it can be an activity; such as a one-hour
long, department meeting from 8:00 AM to 9:00 AM, tomorrow.
Generally, an event will take up time on an individual calendar.
Hence, the event will appear as an opaque interval in a search for
busy time. Alternately, the event can have its Time Transparency
set to "TRANSPARENT" in order to prevent blocking of the event in
searches for busy time.

The "VEVENT" is also the calendar component used to specify an
anniversary or daily reminder within a calendar. These events
have a DATE value type for the "DTSTART" property instead of the
default value type of DATE-TIME. If such a "VEVENT" has a "DTEND"
property, it MUST be specified as a DATE value also. The
anniversary type of "VEVENT" can span more than one date (i.e.,
"DTEND" property value is set to a calendar date after the
"DTSTART" property value). If such a "VEVENT" has a "DURATION"
property, it MUST be specified as a "dur-day" or "dur-week" value.

The "DTSTART" property for a "VEVENT" specifies the inclusive
start of the event. For recurring events, it also specifies the
very first instance in the recurrence set. The "DTEND" property
for a "VEVENT" calendar component specifies the non-inclusive end
of the event. For cases where a "VEVENT" calendar component
specifies a "DTSTART" property with a DATE value type but no
"DTEND" nor "DURATION" property, the event's duration is taken to
be one day. For cases where a "VEVENT" calendar component
specifies a "DTSTART" property with a DATE-TIME value type but no
"DTEND" property, the event ends on the same calendar date and
time of day specified by the "DTSTART" property.

The "VEVENT" calendar component cannot be nested within another
calendar component. However, "VEVENT" calendar components can be
related to each other or to a "VTODO" or to a "VJOURNAL" calendar
component with the "RELATED-TO" property.

Example: The following is an example of the "VEVENT" calendar
component used to represent a meeting that will also be opaque to
searches for busy time:

BEGIN:VEVENT
UID:19970901T130000Z-123401@example.com
DTSTAMP:19970901T130000Z
DTSTART:19970903T163000Z
DTEND:19970903T190000Z
SUMMARY:Annual Employee Review
CLASS:PRIVATE
CATEGORIES:BUSINESS,HUMAN RESOURCES
END:VEVENT

The following is an example of the "VEVENT" calendar component
used to represent a reminder that will not be opaque, but rather
transparent, to searches for busy time:

BEGIN:VEVENT
UID:19970901T130000Z-123402@example.com
DTSTAMP:19970901T130000Z
DTSTART:19970401T163000Z
DTEND:19970402T010000Z
SUMMARY:Laurel is in sensitivity awareness class.
CLASS:PUBLIC
CATEGORIES:BUSINESS,HUMAN RESOURCES
TRANSP:TRANSPARENT
END:VEVENT

The following is an example of the "VEVENT" calendar component
used to represent an anniversary that will occur annually. annually:

BEGIN:VEVENT
UID:19970901T130000Z-123403@example.com
DTSTAMP:19970901T130000Z
DTSTART;VALUE=DATE:19971102
SUMMARY:Our Blissful Anniversary
TRANSP:TRANSPARENT
CLASS:CONFIDENTIAL
CATEGORIES:ANNIVERSARY,PERSONAL,SPECIAL OCCASION
RRULE:FREQ=YEARLY
END:VEVENT

The following is an example of the "VEVENT" calendar component
used to represent a multi-day event scheduled from June 28th, 2007
to July 8th, 2007 inclusively. Note that the "DTEND" property is
set to July 9th, 2007, since the "DTEND" property specifies the
non-inclusive end of the event.

BEGIN:VEVENT
UID:20070423T123432Z-541111@example.com
DTSTAMP:20070423T123432Z
DTSTART;VALUE=DATE:20070628
DTEND;VALUE=DATE:20070709
SUMMARY:Festival International de Jazz de Montreal
TRANSP:TRANSPARENT
END:VEVENT

3.6.2. To-do To-Do Component

Component Name: VTODO

Purpose: Provide a grouping of calendar properties that describe a
to-do.

Format Definition: A "VTODO" calendar component is defined by the
following notation:

todoc = "BEGIN" ":" "VTODO" CRLF
todoprop *alarmc
"END" ":" "VTODO" CRLF

todoprop = *(
;
; the The following are REQUIRED,
; but MUST NOT occur more than once once.
;
dtstamp / uid /
;
; the The following are OPTIONAL,
; but MUST NOT occur more than once once.
;
class / completed / created / description /
dtstart / geo / last-mod / location / organizer /
percent / priority / recurid / seq / status /
summary / url /
;
; the The following is OPTIONAL,
; but SHOULD NOT occur more than once once.
;
rrule /
;
; either Either 'due' or 'duration' MAY appear in
; a 'todoprop', but 'due' and 'duration'
; MUST NOT occur in the same 'todoprop'.
; If 'duration' appear in a 'todoprop',
; then 'dtstart' MUST also appear in
; the same 'todoprop'.
;
due / duration /
;
; the The following are OPTIONAL,
; and MAY occur more than once once.
;
attach / attendee / categories / comment / contact /
exdate / rstatus / related / resources /
rdate / x-prop / iana-prop
;
)

Description: A "VTODO" calendar component is a grouping of component
properties and possibly "VALARM" calendar components that
represent an action-item or assignment. For example, it can be
used to represent an item of work assigned to an individual; such
as "turn in travel expense today".

The "VTODO" calendar component cannot be nested within another
calendar component. However, "VTODO" calendar components can be
related to each other or to a "VEVENT" or to a "VJOURNAL" calendar
component with the "RELATED-TO" property.

A "VTODO" calendar component without the "DTSTART" and "DUE" (or
"DURATION") properties specifies a to-do that will be associated
with each successive calendar date, until it is completed.

Examples: The following is an example of a "VTODO" calendar
component that needs to be completed before May 1st, 2007. On
midnight May 1st, 2007 this to-do would be considered overdue.

BEGIN:VTODO
UID:20070313T123432Z-456553@example.com
DTSTAMP:20070313T123432Z
DUE;VALUE=DATE:20070501
SUMMARY:Submit Quebec Income Tax Return for 2006
CLASS:CONFIDENTIAL
CATEGORIES:FAMILY,FINANCE
STATUS:NEEDS-ACTION
END:VTODO

The following is an example of a "VTODO" calendar component that
was due before 1:00 P.M. UTC on July 9th, 2007 and was completed
on July 7th, 2007 at 10:00 A.M. UTC.

BEGIN:VTODO
UID:20070514T103211Z-123404@example.com
DTSTAMP:20070514T103211Z
DTSTART:20070514T110000Z
DUE:20070709T130000Z
COMPLETED:20070707T100000Z
SUMMARY:Submit Revised Internet-Draft
PRIORITY:1
STATUS:NEEDS-ACTION
END:VTODO

3.6.3. Journal Component

Component Name: VJOURNAL

Purpose: Provide a grouping of component properties that describe a
journal entry.

Format Definition: A "VJOURNAL" calendar component is defined by the
following notation:

journalc = "BEGIN" ":" "VJOURNAL" CRLF
jourprop
"END" ":" "VJOURNAL" CRLF

jourprop = *(
;
; the The following are REQUIRED,
; but MUST NOT occur more than once once.
;
dtstamp / uid /
;
; the The following are OPTIONAL,
; but MUST NOT occur more than once once.
;
class / created / dtstart /
last-mod / organizer / recurid / seq /
status / summary / url /
;
; the The following is OPTIONAL,
; but SHOULD NOT occur more than once once.
;
rrule /
;
; the The following are OPTIONAL,
; and MAY occur more than once once.
;
attach / attendee / categories / comment /
contact / description / exdate / related / rdate /
rstatus / x-prop / iana-prop
;
)

Description: A "VJOURNAL" calendar component is a grouping of
component properties that represent one or more descriptive text
notes associated with a particular calendar date. The "DTSTART"
property is used to specify the calendar date that with which the
journal entry is associated with. associated. Generally, it will have a DATE value
data type, but it can also be used to specify a DATE-TIME value
data type. Examples of a journal entry include a daily record of
a legislative body or a journal entry of individual telephone
contacts for the day or an ordered list of accomplishments for the
day. The "VJOURNAL" calendar component can also be used to
associate a document with a calendar date.

The "VJOURNAL" calendar component does not take up time on a
calendar. Hence, it does not play a role in free or busy time
searches -- it is as though it has a time transparency value of
TRANSPARENT. It is transparent to any such searches.

The "VJOURNAL" calendar component cannot be nested within another
calendar component. However, "VJOURNAL" calendar components can
be related to each other or to a "VEVENT" or to a "VTODO" calendar
component, with the "RELATED-TO" property.

Example: The following is an example of the "VJOURNAL" calendar
component:

BEGIN:VJOURNAL
UID:19970901T130000Z-123405@example.com
DTSTAMP:19970901T130000Z
DTSTART;VALUE=DATE:19970317
SUMMARY:Staff meeting minutes
DESCRIPTION:1. Staff meeting: Participants include Joe\, Lisa
Lisa\, and Bob. Aurora project plans were reviewed.
There is currentl
y currently no budget reserves for this project.
Lisa will escalate to management. Next meeting on Tuesday.\n
2. Telephone Conference: ABC Corp. sales representative
called to discuss new printer. Promised to get us a demo by Friday.\n
3.
Friday.\n3. Henry Miller (Handsoff Insurance): Car was
totaled by tree. Is looking into a loaner car. 555-2323
(tel).
END:VJOURNAL

3.6.4. Free/Busy Component

Component Name: VFREEBUSY

Purpose: Provide a grouping of component properties that describe
either a request for free/busy time, describe a response to a
request for free/busy time time, or describe a published set of busy
time.

Format Definition: A "VFREEBUSY" calendar component is defined by
the following notation:

freebusyc = "BEGIN" ":" "VFREEBUSY" CRLF
fbprop
"END" ":" "VFREEBUSY" CRLF

fbprop = *(
;
; the The following are REQUIRED,
; but MUST NOT occur more than once once.
;
dtstamp / uid /
;
; the The following are OPTIONAL,
; but MUST NOT occur more than once once.
;
contact / dtstart / dtend /
organizer / url /
;
; the The following are OPTIONAL,
; and MAY occur more than once once.
;
attendee / comment / freebusy / rstatus / x-prop /
iana-prop
;
)

Description: A "VFREEBUSY" calendar component is a grouping of
component properties that represents either a request for, for free or
busy time information, a reply to a request for free or busy time information
information, or a published set of busy time information.

When used to request free/busy time information, the "ATTENDEE"
property specifies the calendar users whose free/busy time is
being requested; the "ORGANIZER" property specifies the calendar
user who is requesting the free/busy time; the "DTSTART" and
"DTEND" properties specify the window of time for which the free/
busy time is being requested; the "UID" and "DTSTAMP" properties
are specified to assist in proper sequencing of multiple free/busy
time requests.

When used to reply to a request for free/busy time, the "ATTENDEE"
property specifies the calendar user responding to the free/busy
time request; the "ORGANIZER" property specifies the calendar user
that originally requested the free/busy time; the "FREEBUSY"
property specifies the free/busy time information (if it exists);
and the "UID" and "DTSTAMP" properties are specified to assist in
proper sequencing of multiple free/busy time replies.

When used to publish busy time, the "ORGANIZER" property specifies
the calendar user associated with the published busy time; the
"DTSTART" and "DTEND" properties specify an inclusive time window
that surrounds the busy time information; the "FREEBUSY" property
specifies the published busy time information; and the "DTSTAMP"
property specifies the date/time DATE-TIME that iCalendar object was
created.

The "VFREEBUSY" calendar component cannot be nested within another
calendar component. Multiple "VFREEBUSY" calendar components can
be specified within an iCalendar object. This permits the
grouping of Free/Busy free/busy information into logical collections, such
as monthly groups of busy time information.

The "VFREEBUSY" calendar component is intended for use in
iCalendar object methods involving requests for free time,
requests for busy time, requests for both free and busy, and the
associated replies.

Free/Busy information is represented with the "FREEBUSY" property.
This property provides a terse representation of time periods.
One or more "FREEBUSY" properties can be specified in the
"VFREEBUSY" calendar component.

When present in a "VFREEBUSY" calendar component, the "DTSTART"
and "DTEND" properties SHOULD be specified prior to any "FREEBUSY"
properties.

The recurrence properties ("RRULE", "RDATE", "EXDATE") are not
permitted within a "VFREEBUSY" calendar component. Any recurring
events are resolved into their individual busy time periods using
the "FREEBUSY" property.

Example: The following is an example of a "VFREEBUSY" calendar
component used to request free or busy time information:

BEGIN:VFREEBUSY
UID:19970901T082949Z-FA43EF@example.com
ORGANIZER:mailto:jane_doe@example.com
ATTENDEE:mailto:john_public@example.com
DTSTART:19971015T050000Z
DTEND:19971016T050000Z
DTSTAMP:19970901T083000Z
END:VFREEBUSY
The following is an example of a "VFREEBUSY" calendar component
used to reply to the request with busy time information:

BEGIN:VFREEBUSY
UID:19970901T095957Z-76A912@example.com
ORGANIZER:mailto:jane_doe@example.com
ATTENDEE:mailto:john_public@example.com
DTSTAMP:19970901T100000Z
FREEBUSY:19971015T050000Z/PT8H30M,
19971015T160000Z/PT5H30M,19971015T223000Z/PT6H30M
URL:http://example.com/pub/busy/jpublic-01.ifb
COMMENT:This iCalendar file contains busy time information for
the next three months.
END:VFREEBUSY

The following is an example of a "VFREEBUSY" calendar component
used to publish busy time information. information:

BEGIN:VFREEBUSY
UID:19970901T115957Z-76A912@example.com
DTSTAMP:19970901T120000Z
ORGANIZER:jsmith@example.com
DTSTART:19980313T141711Z
DTEND:19980410T141711Z
FREEBUSY:19980314T233000Z/19980315T003000Z
FREEBUSY:19980316T153000Z/19980316T163000Z
FREEBUSY:19980318T030000Z/19980318T040000Z
URL:http://www.example.com/calendar/busytime/jsmith.ifb
END:VFREEBUSY

3.6.5. Time Zone Component

Component Name: VTIMEZONE

Purpose: Provide a grouping of component properties that defines a
time zone.

Format Definition: A "VTIMEZONE" calendar component is defined by
the following notation:

timezonec = "BEGIN" ":" "VTIMEZONE" CRLF
*(
;
; 'tzid' is REQUIRED, but MUST NOT occur more
; than once once.
;
tzid /
;
; 'last-mod' and 'tzurl' are OPTIONAL,
; but MUST NOT occur more than once once.
;
last-mod / tzurl /
;
; one One of 'standardc' or 'daylightc' MUST occur
; and each MAY occur more than once.
;
standardc / daylightc /
;
; the The following are OPTIONAL,
; and MAY occur more than once once.
;
x-prop / iana-prop
;
)
"END" ":" "VTIMEZONE" CRLF

standardc = "BEGIN" ":" "STANDARD" CRLF
tzprop
"END" ":" "STANDARD" CRLF

daylightc = "BEGIN" ":" "DAYLIGHT" CRLF
tzprop
"END" ":" "DAYLIGHT" CRLF

tzprop = *(
;
; the The following are REQUIRED,
; but MUST NOT occur more than once once.
;
dtstart / tzoffsetto / tzoffsetfrom /
;
; the The following is OPTIONAL,
; but SHOULD NOT occur more than once once.
;
rrule /
;
; the The following are OPTIONAL,
; and MAY occur more than once once.
;
comment / rdate / tzname / x-prop / iana-prop
;
)
Description: A time zone is unambiguously defined by the set of time
measurement rules determined by the governing body for a given
geographic area. These rules describe describe, at a minimum minimum, the base
offset from UTC for the time zone, often referred to as the
Standard Time offset. Many locations adjust their Standard Time
forward or backward by one hour, in order to accommodate seasonal
changes in number of daylight hours, often referred to as Daylight
Saving Time. Some locations adjust their time by a fraction of an
hour. Standard Time is also known as Winter Time. Daylight
Saving Time is also known as Advanced Time, Summer Time, or Legal
Time in certain countries. The following table shows the changes
in time zone rules in effect for New York City starting from 1967.
Each line represents a description or rule for a particular
observance.

Effective Observance Rule

+-----------+--------------------------+--------+--------------+
| Date | (Date/Time) (Date-Time) | Offset | Abbreviation |
+-----------+--------------------------+--------+--------------+
| 1967-1973 | last Sun in Apr, 02:00 | -0400 | EDT |
| | | | |
| 1967-2006 | last Sun in Oct, 02:00 | -0500 | EST |
| | | | |
| 1974-1974 | Jan 6, 02:00 | -0400 | EDT |
| | | | |
| 1975-1975 | Feb 23, 02:00 | -0400 | EDT |
| | | | |
| 1976-1986 | last Sun in Apr, 02:00 | -0400 | EDT |
| | | | |
| 1987-2006 | first Sun in Apr, 02:00 | -0400 | EDT |
| | | | |
| 2007-* | second Sun in Mar, 02:00 | -0400 | EDT |
| | | | |
| 2007-* | first Sun in Nov, 02:00 | -0500 | EST |
+-----------+--------------------------+--------+--------------+

Note: The specification of a global time zone registry is not
addressed by this document and is left for future study.
However, implementers may find the TZ database [TZDB] a useful
reference. It is an informal, public-domain collection of time
zone information, which is currently being maintained by
volunteer Internet participants, and is used in several
operating systems. This database contains current and
historical time zone information for a wide variety of
locations around the globe; it provides a time zone identifier
for every unique time zone rule set in actual use since 1970,
with historical data going back to the introduction of standard
time.

Interoperability between two calendaring and scheduling
applications, especially for recurring events, to-dos or journal
entries, is dependent on the ability to capture and convey date
and time information in an unambiguous format. The specification
of current time zone information is integral to this behavior.

If present, the "VTIMEZONE" calendar component defines the set of
Standard Time and Daylight Saving Time observances (or rules) for
a particular time zone for a given interval of time. The
"VTIMEZONE" calendar component cannot be nested within other
calendar components. Multiple "VTIMEZONE" calendar components can
exist in an iCalendar object. In this situation, each "VTIMEZONE"
MUST represent a unique time zone definition. This is necessary
for some classes of events, such as airline flights, that start in
one time zone and end in another.

The "VTIMEZONE" calendar component MUST include the "TZID"
property and at least one definition of a "STANDARD" or "DAYLIGHT"
sub-component. The "STANDARD" or "DAYLIGHT" subcomponent sub-component MUST
include the "DTSTART", "TZOFFSETFROM" "TZOFFSETFROM", and "TZOFFSETTO"
properties.

An individual "VTIMEZONE" calendar component MUST be specified for
each unique "TZID" parameter value specified in the iCalendar
object. In addition, a "VTIMEZONE" calendar component, referred
to by a recurring calendar component, MUST provide valid time zone
information for all recurrence instances.

Each "VTIMEZONE" calendar component consists of a collection of
one or more sub-components that describe the rule for a particular
observance (either a Standard Time or a Daylight Saving Time
observance). The "STANDARD" sub-component consists of a
collection of properties that describe Standard Time. The
"DAYLIGHT" sub-component consists of a collection of properties
that describe Daylight Saving Time. In general general, this collection
of properties consists of:

* the first onset date-time DATE-TIME for the observance;

* the last onset date-time DATE-TIME for the observance, if a last onset is
known;

* the offset to be applied for the observance;
* a rule that describes the day and time when the observance
takes effect;

* an optional name for the observance.

For a given time zone, there may be multiple unique definitions of
the observances over a period of time. Each observance is
described using either a "STANDARD" or "DAYLIGHT" sub-component.
The collection of these sub-components is used to describe the
time zone for a given period of time. The offset to apply at any
given time is found by locating the observance that has the last
onset date and time before the time in question, and using the
offset value from that observance.

The top-level properties in a "VTIMEZONE" calendar component are:

The mandatory "TZID" property is a text value that uniquely
identifies the "VTIMEZONE" calendar component within the scope of
an iCalendar object.

The optional "LAST-MODIFIED" property is a UTC value that
specifies the date and time that this time zone definition was
last updated.

The optional "TZURL" property is a url value that points to a
published "VTIMEZONE" definition. "TZURL" SHOULD refer to a
resource that is accessible by anyone who might need to interpret
the object. This SHOULD NOT normally be a "file" URL or other URL
that is not widely-accessible. widely accessible.

The collection of properties that are used to define the
"STANDARD" and "DAYLIGHT" sub-components include:

The mandatory "DTSTART" property gives the effective onset date
and local time for the time zone sub-component definition.
"DTSTART" in this usage MUST be specified as a date with a local
time value.

The mandatory "TZOFFSETFROM" property gives the UTC offset which that is
in use when the onset of this time zone observance begins.
"TZOFFSETFROM" is combined with "DTSTART" to define the effective
onset for the time zone sub-component definition. For example,
the following represents the time at which the observance of
Standard Time took effect in Fall 1967 for New York City:

DTSTART:19671029T020000

TZOFFSETFROM:-0400
The mandatory "TZOFFSETTO" property gives the UTC offset for the
time zone sub-component (Standard Time or Daylight Saving Time)
when this observance is in use.

The optional "TZNAME" property is the customary name for the time
zone. This could be used for displaying dates.

The onset date-times DATE-TIME values for the observance defined by the time
zone sub-component is defined by the "DTSTART", "RRULE", and
"RDATE" properties.

The "RRULE" property defines the recurrence rule for the onset of
the observance defined by this time zone sub-component. Some
specific requirements for the usage of "RRULE" for this purpose
include:

* If observance is known to have an effective end date, the
"UNTIL" recurrence rule parameter MUST be used to specify the
last valid onset of this observance (i.e., the UNTIL date-time DATE-TIME
will be equal to the last instance generated by the recurrence
pattern). It MUST be specified in UTC time.

* The "DTSTART" and the "TZOFFSETFROM" properties MUST be used
when generating the onset date-time DATE-TIME values (instances) from the
"RRULE".

The "RDATE" property can also be used to define the onset of the
observance by giving the individual onset date and times. "RDATE"
in this usage MUST be specified as a date with local time value,
relative to the UTC offset specified in the "TZOFFSETFROM"
property.

The optional "COMMENT" property is also allowed for descriptive
explanatory text.

Example: The following are examples of the "VTIMEZONE" calendar
component:

This is an example showing all the time zone rules for New York
City since April 30, 1967 at 03:00:00 EDT.

BEGIN:VTIMEZONE
TZID:America/New_York
LAST-MODIFIED:20050809T050000Z
BEGIN:DAYLIGHT
DTSTART:19670430T020000
RRULE:FREQ=YEARLY;BYMONTH=4;BYDAY=-1SU;UNTIL=19730429T070000Z
TZOFFSETFROM:-0500
TZOFFSETTO:-0400
TZNAME:EDT
END:DAYLIGHT
BEGIN:STANDARD
DTSTART:19671029T020000
RRULE:FREQ=YEARLY;BYMONTH=10;BYDAY=-1SU;UNTIL=20061029T060000Z
TZOFFSETFROM:-0400
TZOFFSETTO:-0500
TZNAME:EST
END:STANDARD
BEGIN:DAYLIGHT
DTSTART:19740106T020000
RDATE:19750223T020000
TZOFFSETFROM:-0500
TZOFFSETTO:-0400
TZNAME:EDT
END:DAYLIGHT
BEGIN:DAYLIGHT
DTSTART:19760425T020000
RRULE:FREQ=YEARLY;BYMONTH=4;BYDAY=-1SU;UNTIL=19860427T070000Z
TZOFFSETFROM:-0500
TZOFFSETTO:-0400
TZNAME:EDT
END:DAYLIGHT
BEGIN:DAYLIGHT
DTSTART:19870405T020000
RRULE:FREQ=YEARLY;BYMONTH=4;BYDAY=1SU;UNTIL=20060402T070000Z
TZOFFSETFROM:-0500
TZOFFSETTO:-0400
TZNAME:EDT
END:DAYLIGHT
BEGIN:DAYLIGHT
DTSTART:20070311T020000
RRULE:FREQ=YEARLY;BYMONTH=3;BYDAY=2SU
TZOFFSETFROM:-0500
TZOFFSETTO:-0400
TZNAME:EDT
END:DAYLIGHT
BEGIN:STANDARD
DTSTART:20071104T020000
RRULE:FREQ=YEARLY;BYMONTH=11;BYDAY=1SU
TZOFFSETFROM:-0400
TZOFFSETTO:-0500
TZNAME:EST
END:STANDARD
END:VTIMEZONE
This is an example showing time zone information for New York City
using only the "DTSTART" property. Note that this is only
suitable for a recurring event that starts on or later than March
11, 2007 at 03:00:00 EDT (i.e., the earliest effective transition
date and time) and ends no later than March 9, 2008 at 01:59:59
EST (i.e., latest valid date and time for EST in this scenario).
For example, this can be used for a recurring event that occurs
every Friday, 8:00 A.M.-9:00 A.M., starting June 1, 2007, ending
December 31, 2007,

BEGIN:VTIMEZONE
TZID:America/New_York
LAST-MODIFIED:20050809T050000Z
BEGIN:STANDARD
DTSTART:20071104T020000
TZOFFSETFROM:-0400
TZOFFSETTO:-0500
TZNAME:EST
END:STANDARD
BEGIN:DAYLIGHT
DTSTART:20070311T020000
TZOFFSETFROM:-0500
TZOFFSETTO:-0400
TZNAME:EDT
END:DAYLIGHT
END:VTIMEZONE

This is a simple example showing the current time zone rules for
New York City using a "RRULE" recurrence pattern. Note that there
is no effective end date to either of the Standard Time or
Daylight Time rules. This information would be valid for a
recurring event starting today and continuing indefinitely.

BEGIN:VTIMEZONE
TZID:America/New_York
LAST-MODIFIED:20050809T050000Z
TZURL:http://zones.example.com/tz/America-New_York.ics
BEGIN:STANDARD
DTSTART:20071104T020000
RRULE:FREQ=YEARLY;BYMONTH=11;BYDAY=1SU
TZOFFSETFROM:-0400
TZOFFSETTO:-0500
TZNAME:EST
END:STANDARD
BEGIN:DAYLIGHT
DTSTART:20070311T020000
RRULE:FREQ=YEARLY;BYMONTH=3;BYDAY=2SU
TZOFFSETFROM:-0500
TZOFFSETTO:-0400
TZNAME:EDT
END:DAYLIGHT
END:VTIMEZONE

This is an example showing a set of rules for a fictitious time
zone where the Daylight Time rule has an effective end date (i.e.,
after that date, Daylight Time is no longer observed).

BEGIN:VTIMEZONE
TZID:Fictitious
LAST-MODIFIED:19870101T000000Z
BEGIN:STANDARD
DTSTART:19671029T020000
RRULE:FREQ=YEARLY;BYDAY=-1SU;BYMONTH=10
TZOFFSETFROM:-0400
TZOFFSETTO:-0500
TZNAME:EST
END:STANDARD
BEGIN:DAYLIGHT
DTSTART:19870405T020000
RRULE:FREQ=YEARLY;BYDAY=1SU;BYMONTH=4;UNTIL=19980404T070000Z
TZOFFSETFROM:-0500
TZOFFSETTO:-0400
TZNAME:EDT
END:DAYLIGHT
END:VTIMEZONE

This is an example showing a set of rules for a fictitious time
zone where the first Daylight Time rule has an effective end date.
There is a second Daylight Time rule that picks up where the other
left off.

3.6.6. Alarm Component

Component Name: VALARM

Purpose: Provide a grouping of component properties that define an
alarm.

Format Definition: A "VALARM" calendar component is defined by the
following notation:

alarmc = "BEGIN" ":" "VALARM" CRLF
(audioprop / dispprop / emailprop)
"END" ":" "VALARM" CRLF

audioprop = *(
;
; 'action' and 'trigger' are both REQUIRED,
; but MUST NOT occur more than once once.
;
action / trigger /
;
; 'duration' and 'repeat' are both OPTIONAL,
; and MUST NOT occur more than once each, each;
; but if one occurs, so MUST the other other.
;
duration / repeat /
;
; the The following is OPTIONAL,
; but MUST NOT occur more than once once.
;
attach /
;
; the The following is OPTIONAL,
; and MAY occur more than once once.
;
x-prop / iana-prop
;
)

dispprop = *(
;
; the The following are REQUIRED,
; but MUST NOT occur more than once once.
;
action / description / trigger /
;
; 'duration' and 'repeat' are both OPTIONAL,
; and MUST NOT occur more than once each, each;
; but if one occurs, so MUST the other other.
;
duration / repeat /
;
; the The following is OPTIONAL,
; and MAY occur more than once once.
;
x-prop / iana-prop
;
)

emailprop = *(
;
; the The following are all REQUIRED,
; but MUST NOT occur more than once once.
;
action / description / trigger / summary /
;
; the The following is REQUIRED,
; and MAY occur more than once once.
;
attendee /
;
; 'duration' and 'repeat' are both OPTIONAL,
; and MUST NOT occur more than once each, each;
; but if one occurs, so MUST the other other.
;
duration / repeat /
;
; the The following are OPTIONAL,
; and MAY occur more than once once.
;
attach / x-prop / iana-prop
;
)

Description: A "VALARM" calendar component is a grouping of
component properties that is a reminder or alarm for an event or a
to-do. For example, it may be used to define a reminder for a
pending event or an overdue to-do.

The "VALARM" calendar component MUST include the "ACTION" and
"TRIGGER" properties. The "ACTION" property further constrains
the "VALARM" calendar component in the following ways:

When the action is "AUDIO", the alarm can also include one and
only one "ATTACH" property, which MUST point to a sound resource,
which is rendered when the alarm is triggered.

When the action is "DISPLAY", the alarm MUST also include a
"DESCRIPTION" property, which contains the text to be displayed
when the alarm is triggered.

When the action is "EMAIL", the alarm MUST include a "DESCRIPTION"
property, which contains the text to be used as the message body,
a "SUMMARY" property, which contains the text to be used as the
message subject, and one or more "ATTENDEE" properties, which
contain the email address of attendees to receive the message. It
can also include one or more "ATTACH" properties, which are
intended to be sent as message attachments. When the alarm is
triggered, the email message is sent.

The "VALARM" calendar component MUST only appear within either a
"VEVENT" or "VTODO" calendar component. "VALARM" calendar
components cannot be nested. Multiple mutually independent
"VALARM" calendar components can be specified for a single
"VEVENT" or "VTODO" calendar component.

The "TRIGGER" property specifies when the alarm will be triggered.
The "TRIGGER" property specifies a duration prior to the start of
an event or a to-do. The "TRIGGER" edge may be explicitly set to
be relative to the "START" or "END" of the event or to-do with the
"RELATED" parameter of the "TRIGGER" property. The "TRIGGER"
property value type can alternatively be set to an absolute
calendar date with UTC time.

In an alarm set to trigger on the "START" of an event or to-do,
the "DTSTART" property MUST be present in the associated event or
to-do. In an alarm in a "VEVENT" calendar component set to
trigger on the "END" of the event, either the "DTEND" property
MUST be present, or the "DTSTART" and "DURATION" properties MUST
both be present. In an alarm in a "VTODO" calendar component set
to trigger on the "END" of the to-do, either the "DUE" property
MUST be present, or the "DTSTART" and "DURATION" properties MUST
both be present.

The alarm can be defined such that it triggers repeatedly. A
definition of an alarm with a repeating trigger MUST include both
the "DURATION" and "REPEAT" properties. The "DURATION" property
specifies the delay period, after which the alarm will repeat.
The "REPEAT" property specifies the number of additional
repetitions that the alarm will be triggered. This repetition
count is in addition to the initial triggering of the alarm. Both
of these properties MUST be present in order to specify a
repeating alarm. If one of these two properties is absent, then
the alarm will not repeat beyond the initial trigger.

The "ACTION" property is used within the "VALARM" calendar
component to specify the type of action invoked when the alarm is
triggered. The "VALARM" properties provide enough information for
a specific action to be invoked. It is typically the
responsibility of a "Calendar User Agent" (CUA) to deliver the
alarm in the specified fashion. An "ACTION" property value of
AUDIO specifies an alarm that causes a sound to be played to alert
the user; DISPLAY specifies an alarm that causes a text message to
be displayed to the user; and EMAIL specifies an alarm that causes
an electronic email message to be delivered to one or more email
addresses.

In an AUDIO alarm, if the optional "ATTACH" property is included,
it MUST specify an audio sound resource. The intention is that
the sound will be played as the alarm effect. If an "ATTACH"
property is specified that does not refer to a sound resource, or
if the specified sound resource cannot be rendered (because its
format is unsupported, or because it cannot be retrieved), then
the CUA or other entity responsible for playing the sound may
choose a fallback action, such as playing a built-in default
sound, or playing no sound at all.

In a DISPLAY alarm, the intended alarm effect is for the text
value of the "DESCRIPTION" property to be displayed to the user.

In an EMAIL alarm, the intended alarm effect is for an email
message to be composed and delivered to all the addresses
specified by the "ATTENDEE" properties in the "VALARM" calendar
component. The "DESCRIPTION" property of the "VALARM" calendar
component MUST be used as the body text of the message, and the
"SUMMARY" property MUST be used as the subject text. Any "ATTACH"
properties in the "VALARM" calendar component SHOULD be sent as
attachments to the message.

Note: Implementations should carefully consider whether they
accept alarm components from untrusted sources, e.g., when
importing calendar objects from external sources. One
reasonable policy is to always ignore alarm components that the
calendar user has not set herself, or at least ask for
confirmation in such a case.

Example: The following example is for a "VALARM" calendar component
that specifies an audio alarm that will sound at a precise time
and repeat 4 more times at 15 minute 15-minute intervals:

BEGIN:VALARM
TRIGGER;VALUE=DATE-TIME:19970317T133000Z
REPEAT:4
DURATION:PT15M
ACTION:AUDIO
ATTACH;FMTTYPE=audio/basic:ftp://example.com/pub/
sounds/bell-01.aud
END:VALARM

The following example is for a "VALARM" calendar component that
specifies a display alarm that will trigger 30 minutes before the
scheduled start of the event or of the to-do it is associated with
and will repeat 2 more times at 15 minute 15-minute intervals:

BEGIN:VALARM
TRIGGER:-PT30M
REPEAT:2
DURATION:PT15M
ACTION:DISPLAY
DESCRIPTION:Breakfast meeting with executive\n
team at 8:30 AM EST.
END:VALARM
The following example is for a "VALARM" calendar component that
specifies an email alarm that will trigger 2 days before the
scheduled due date/time DATE-TIME of a to-do with which it is associated with. associated.
It does not repeat. The email has a subject, body body, and attachment
link.

BEGIN:VALARM
TRIGGER;RELATED=END:-P2D
ACTION:EMAIL
ATTENDEE:mailto:john_doe@example.com
SUMMARY:*** REMINDER: SEND AGENDA FOR WEEKLY STAFF MEETING ***
DESCRIPTION:A draft agenda needs to be sent out to the attendees
to the weekly managers meeting (MGR-LIST). Attached is a
pointer the document template for the agenda file.
ATTACH;FMTTYPE=application/msword:http://example.com/
templates/agenda.doc
END:VALARM

3.7. Calendar Properties

The Calendar Properties are attributes that apply to the iCalendar
object, as a whole. These properties do not appear within a calendar
component. They SHOULD be specified after the "BEGIN:VCALENDAR"
delimiter string and prior to any calendar component.

3.7.1. Calendar Scale

Property Name: CALSCALE

Purpose: This property defines the calendar scale used for the
calendar information specified in the iCalendar object.

Value Type: TEXT

Property Parameters: IANA and non-standard property parameters can
be specified on this property.

Conformance: This property can be specified once in an iCalendar
object. The default value is "GREGORIAN".

Description: This memo is based on the Gregorian calendar scale.
The Gregorian calendar scale is assumed if this property is not
specified in the iCalendar object. It is expected that other
calendar scales will be defined in other specifications or by
future versions of this memo.

Format Definition: This property is defined by the following
notation:

calscale = "CALSCALE" calparam ":" calvalue CRLF

calparam = *(";" other-param)

calvalue = "GREGORIAN"

Example: The following is an example of this property:

CALSCALE:GREGORIAN

3.7.2. Method

Property Name: METHOD

Purpose: This property defines the iCalendar object method
associated with the calendar object.

Value Type: TEXT

Property Parameters: IANA and non-standard property parameters can
be specified on this property.

Conformance: This property can be specified once in an iCalendar
object.

Description: When used in a MIME message entity, the value of this
property MUST be the same as the Content-Type "method" parameter
value. If either the "METHOD" property or the Content-Type
"method" parameter is specified, then the other MUST also be
specified.

No methods are defined by this specification. This is the subject
of other specifications, such as the iCalendar Transport-
independent Interoperability Protocol (iTIP) defined by
[I-D.ietf-calsify-2446bis]. [2446bis].

If this property is not present in the iCalendar object, then a
scheduling transaction MUST NOT be assumed. In such cases, the
iCalendar object is merely being used to transport a snapshot of
some calendar information; without the intention of conveying a
scheduling semantic.

Format Definition: This property is defined by the following
notation:

method = "METHOD" metparam ":" metvalue CRLF

metparam = *(";" other-param)

metvalue = iana-token

Example: The following is a hypothetical example of this property to
convey that the iCalendar object is a scheduling request:

METHOD:REQUEST

3.7.3. Product Identifier

Property Name: PRODID

Purpose: This property specifies the identifier for the product that
created the iCalendar object.

Value Type: TEXT

Property Parameters: IANA and non-standard property parameters can
be specified on this property.

Conformance: The property MUST be specified once in an iCalendar
object.

Description: The vendor of the implementation SHOULD assure that
this is a globally unique identifier; using some technique such as
an FPI value, as defined in [ISO.9070.1991].

This property SHOULD NOT be used to alter the interpretation of an
iCalendar object beyond the semantics specified in this memo. For
example, it is not to be used to further the understanding of non-
standard properties.

Format Definition: This property is defined by the following
notation:

prodid = "PRODID" pidparam ":" pidvalue CRLF

pidparam = *(";" other-param)

pidvalue = text
;Any text that describes the product and version
;and that is generally assured of being unique.

Example: The following is an example of this property. It does not
imply that English is the default language.

PRODID:-//ABC Corporation//NONSGML My Product//EN

3.7.4. Version

Property Name: VERSION

Purpose: This property specifies the identifier corresponding to the
highest version number or the minimum and maximum range of the
iCalendar specification that is required in order to interpret the
iCalendar object.

Value Type: TEXT

Property Parameters: IANA and non-standard property parameters can
be specified on this property.

Conformance: This property MUST be specified once in an iCalendar
object.

Description: A value of "2.0" corresponds to this memo.

Format Definition: This property is defined by the following
notation:

version = "VERSION" verparam ":" vervalue CRLF

verparam = *(";" other-param)

vervalue = "2.0" ;This memo
/ maxver
/ (minver ";" maxver)

minver = <A IANA registered IANA-registered iCalendar version identifier>
;Minimum iCalendar version needed to parse the iCalendar object object.

maxver = <A IANA registered IANA-registered iCalendar version identifier>
;Maximum iCalendar version needed to parse the iCalendar object object.

Example: The following is an example of this property:

VERSION:2.0

3.8. Component Properties

The following properties can appear within calendar components, as
specified by each component property definition.

3.8.1. Descriptive Component Properties

The following properties specify descriptive information about
calendar components.

3.8.1.1. Attachment

Property Name: ATTACH

Purpose: This property provides the capability to associate a
document object with a calendar component.

Value Type: The default value type for this property is URI. The
value type can also be set to BINARY to indicate inline binary
encoded content information.

Property Parameters: IANA, non-standard, inline encoding encoding, and value
data type property parameters can be specified on this property.
The format type parameter can be specified on this property and is
RECOMMENDED for inline binary encoded content information.

Conformance: This property can be specified multiple times in a
"VEVENT", "VTODO", "VJOURNAL" "VJOURNAL", or "VALARM" calendar component with
the exception of AUDIO alarm which that only allows this property to
occur once . once.

Description: This property is used in "VEVENT", "VTODO", and
"VJOURNAL" calendar components to associate a resource (e.g.,
document) with the calendar component. This property is used in
"VALARM" calendar components to specify an audio sound resource or
an email message attachment. This property can be specified as a
URI pointing to a resource or as inline binary encoded content.

When this property is specified as inline binary encoded content,
calendar applications MAY attempt to guess the media type of the
resource via inspection of its content if and only if the media
type of the resource is not given by the "FMTTYPE" parameter. If
the media type remains unknown, calendar applications SHOULD treat
it as type "application/octet-stream".

Format Definition: This property is defined by the following
notation:

attach = "ATTACH" attachparam ( ":" uri ) /
(
";" "ENCODING" "=" "BASE64"
";" "VALUE" "=" "BINARY"
":" binary
)
CRLF

attachparam = *(
;
; the The following is OPTIONAL for a URI value value,
; and RECOMMENDED for a BINARY value,
; and MUST NOT occur more than once once.
;
(";" fmttypeparam) /
;
; the The following is OPTIONAL,
; and MAY occur more than once once.
;
(";" other-param)
;
)

Example: The following are examples of this property:

ATTACH:CID:jsmith.part3.960817T083000.xyzMail@example.com

ATTACH;FMTTYPE=application/postscript:ftp://example.com/pub/
reports/r-960812.ps

3.8.1.2. Categories

Property Name: CATEGORIES

Purpose: This property defines the categories for a calendar
component.

Value Type: TEXT

Property Parameters: IANA, non-standard, and language property
parameters can be specified on this property.

Conformance: The property can be specified within "VEVENT", "VTODO" "VTODO",
or "VJOURNAL" calendar components.

Description: This property is used to specify categories or subtypes
of the calendar component. The categories are useful in searching
for a calendar component of a particular type and category.
Within the "VEVENT", "VTODO" "VTODO", or "VJOURNAL" calendar components,
more than one category can be specified as a COMMA-separated list
of categories
separated by the COMMA character (US-ASCII decimal 44). categories.

Format Definition: This property is defined by the following
notation:

categories = "CATEGORIES" catparam ":" text *("," text)
CRLF

catparam = *(
;
; the The following is OPTIONAL,
; but MUST NOT occur more than once once.
;
(";" languageparam ) /
;
; the The following is OPTIONAL,
; and MAY occur more than once once.
;
(";" other-param)
;
)

Example: The following are examples of this property:

CATEGORIES:APPOINTMENT,EDUCATION

CATEGORIES:MEETING

3.8.1.3. Classification

Property Name: CLASS

Purpose: This property defines the access classification for a
calendar component.

Value Type: TEXT
Property Parameters: IANA and non-standard property parameters can
be specified on this property.

Conformance: The property can be specified once in a "VEVENT",
"VTODO"
"VTODO", or "VJOURNAL" calendar components.

Description: An access classification is only one component of the
general security system within a calendar application. It
provides a method of capturing the scope of the access the
calendar owner intends for information within an individual
calendar entry. The access classification of an individual
iCalendar component is useful when measured along with the other
security components of a calendar system (e.g., calendar user
authentication, authorization, access rights, access role, etc.).
Hence, the semantics of the individual access classifications
cannot be completely defined by this memo alone. Additionally,
due to the "blind" nature of most exchange processes using this
memo, these access classifications cannot serve as an enforcement
statement for a system receiving an iCalendar object. Rather,
they provide a method for capturing the intention of the calendar
owner for the access to the calendar component. If not specified
in a component that allows this property, the default value is
PUBLIC. Applications MUST treat x-name and iana-token value values they
don't recognized recognize the same way as they would the PRIVATE value.

Format Definition: This property is defined by the following
notation:

class = "CLASS" classparam ":" classvalue CRLF

classparam = *(";" other-param)

classvalue = "PUBLIC" / "PRIVATE" / "CONFIDENTIAL" / iana-token
/ x-name
;Default is PUBLIC

Example: The following is an example of this property:

CLASS:PUBLIC

3.8.1.4. Comment

Property Name: COMMENT

Purpose: This property specifies non-processing information intended
to provide a comment to the calendar user.

Value Type: TEXT

Property Parameters: IANA, non-standard, alternate text
representation
representation, and language property parameters can be specified
on this property.

Conformance: This property can be specified multiple times in
"VEVENT", "VTODO", "VJOURNAL", and "VFREEBUSY" calendar components
as well as in the "STANDARD" and "DAYLIGHT" sub-components.

Description: This property is used to specify a comment to the
calendar user.

Format Definition: This property is defined by the following
notation:

comment = "COMMENT" commparam ":" text CRLF

commparam = *(
;
; the The following are OPTIONAL,
; but MUST NOT occur more than once once.
;
(";" altrepparam) / (";" languageparam) /
;
; the The following is OPTIONAL,
; and MAY occur more than once once.
;
(";" other-param)
;
)

Example: The following is an example of this property:

COMMENT:The meeting really needs to include both ourselves
and the customer. We can't hold this meeting without them.
As a matter of fact\, the venue for the meeting ought to be at
their site. - - John

3.8.1.5. Description

Property Name: DESCRIPTION

Purpose: This property provides a more complete description of the
calendar component, component than that provided by the "SUMMARY" property.

Value Type: TEXT

Property Parameters: IANA, non-standard, alternate text
representation
representation, and language property parameters can be specified
on this property.

Conformance: The property can be specified in the "VEVENT", "VTODO",
"VJOURNAL"
"VJOURNAL", or "VALARM" calendar components. The property can be
specified multiple times only within a "VJOURNAL" calendar
component.

Description: This property is used in the "VEVENT" and "VTODO" to
capture lengthy textual decriptions descriptions associated with the activity.

This property is used in the "VJOURNAL" calendar component to
capture one or more textual journal entries.

This property is used in the "VALARM" calendar component to
capture the display text for a DISPLAY category of alarm, and to
capture the body text for an EMAIL category of alarm.

Format Definition: This property is defined by the following
notation:

description = "DESCRIPTION" descparam ":" text CRLF

descparam = *(
;
; the The following are OPTIONAL,
; but MUST NOT occur more than once once.
;
(";" altrepparam) / (";" languageparam) /
;
; the The following is OPTIONAL,
; and MAY occur more than once once.
;
(";" other-param)
;
)

Example: The following is an example of this property with formatted
line breaks in the property value:

DESCRIPTION:Meeting to provide technical review for "Phoenix"
design.\nHappy Face Conference Room. Phoenix design team
MUST attend this meeting.\nRSVP to team leader.

3.8.1.6. Geographic Position

Property Name: GEO

Purpose: This property specifies information related to the global
position for the activity specified by a calendar component.

Value Type: FLOAT. The value MUST be two SEMICOLON separated SEMICOLON-separated FLOAT
values.

Property Parameters: IANA and non-standard property parameters can
be specified on this property.

Conformance: This property can be specified in "VEVENT" or "VTODO"
calendar components.

Description: This property value specifies latitude and longitude,
in that order (i.e., "LAT LON" ordering). The longitude
represents the location East east or West west of the prime meridian as a
positive or negative real number, respectively. The longitude and
latitude values MAY be specified up to six decimal places, which
will allow for accuracy to within one meter of geographical
position. Receiving applications MUST accept values of this
precision and MAY truncate values of greater precision.

Values for latitude and longitude shall be expressed as decimal
fractions of degrees. Whole degrees of latitude shall be
represented by a two-digit decimal number ranging from 0 through
90. Whole degrees of longitude shall be represented by a decimal
number ranging from 0 through 180. When a decimal fraction of a
degree is specified, it shall be separated from the whole number
of degrees by a decimal point.

Latitudes North north of the equator shall be specified by a plus sign
(+), or by the absence of a minus sign (-), preceding the digits
designating degrees. Latitudes South south of the Equator shall be
designated by a minus sign (-) preceding the digits designating
degrees. A point on the Equator shall be assigned to the Northern
Hemisphere.

Longitudes east of the prime meridian shall be specified by a plus
sign (+), or by the absence of a minus sign (-), preceding the
digits designating degrees. Longitudes west of the meridian shall
be designated by minus sign (-) preceding the digits designating
degrees. A point on the prime meridian shall be assigned to the
Eastern Hemisphere. A point on the 180th meridian shall be
assigned to the Western Hemisphere. One exception to this last
convention is permitted. For the special condition of describing
a band of latitude around the earth, the East Bounding Coordinate
data element shall be assigned the value +180 (180) degrees.

Any spatial address with a latitude of +90 (90) or -90 degrees
will specify the position at the North or South Pole,
respectively. The component for longitude may have any legal
value.

With the exception of the special condition described above, this
form is specified in Department of Commerce, 1986, Representation
of geographic point locations for information interchange (Federal
Information Processing Standard 70-1): Washington, Department of
Commerce, National Institute of Standards and Technology. [ANSI INCITS 61-1986].

The simple formula for converting degrees-minutes-seconds into
decimal degrees is:

decimal = degrees + minutes/60 + seconds/3600.

Format Definition: This property is defined by the following
notation:

geo = "GEO" geoparam ":" geovalue CRLF

geoparam = *(";" other-param)

geovalue = float ";" float
;Latitude and Longitude components

Example: The following is an example of this property:

GEO:37.386013;-122.082932

3.8.1.7. Location

Property Name: LOCATION

Purpose: This property defines the intended venue for the activity
defined by a calendar component.

Value Type: TEXT

Property Parameters: IANA, non-standard, alternate text
representation
representation, and language property parameters can be specified
on this property.

Conformance: This property can be specified in "VEVENT" or "VTODO"
calendar component.

Description: Specific venues such as conference or meeting rooms may
be explicitly specified using this property. An alternate
representation may be specified that is a URI that points to
directory information with more structured specification of the
location. For example, the alternate representation may specify
either an LDAP URL [RFC4516] pointing to an LDAP server entry or a
CID URL [RFC2392] pointing to a MIME body part containing a vCard
Virtual-Information Card (vCard) [RFC2426] for the location.

Format Definition: This property is defined by the following
notation:

location = "LOCATION" locparam ":" text CRLF

locparam = *(
;
; the The following are OPTIONAL,
; but MUST NOT occur more than once once.
;
(";" altrepparam) / (";" languageparam) /
;
; the The following is OPTIONAL,
; and MAY occur more than once once.
;
(";" other-param)
;
)

Example: The following are some examples of this property:

LOCATION:Conference Room - F123\, Bldg. 002

LOCATION;ALTREP="http://xyzcorp.com/conf-rooms/f123.vcf":
Conference Room - F123\, Bldg. 002

3.8.1.8. Percent Complete

Property Name: PERCENT-COMPLETE

Purpose: This property is used by an assignee or delegatee of a
to-do to convey the percent completion of a to-do to the
"Organizer".

Value Type: INTEGER
Property Parameters: IANA and non-standard property parameters can
be specified on this property.

Conformance: This property can be specified once in a "VTODO"
calendar component.

Description: The property value is a positive integer between zero 0 and one hundred.
100. A value of "0" indicates the to-do has not yet been started.
A value of "100" indicates that the to-do has been completed.
Integer values in between indicate the percent partially complete.

When a to-do is assigned to multiple individuals, the property
value indicates the percent complete for that portion of the to-do
assigned to the assignee or delegatee. For example, if a to-do is
assigned to both individuals "A" and "B". A reply from "A" with a
percent complete of "70" indicates that "A" has completed 70% of
the to-do assigned to them. A reply from "B" with a percent
complete of "50" indicates "B" has completed 50% of the to-do
assigned to them.

Format Definition: This property is defined by the following
notation:

percent = "PERCENT-COMPLETE" pctparam ":" integer CRLF

pctparam = *(";" other-param)

Example: The following is an example of this property to show 39%
completion:

PERCENT-COMPLETE:39

3.8.1.9. Priority

Property Name: PRIORITY

Purpose: This property defines the relative priority for a calendar
component.

Value Type: INTEGER

Property Parameters: IANA and non-standard property parameters can
be specified on this property.

Conformance: This property can be specified in "VEVENT" and "VTODO"
calendar components.

Description: This priority is specified as an integer in the range
zero 0
to nine. 9. A value of zero (US-ASCII decimal 48) 0 specifies an undefined priority. A value of one (US-ASCII decimal 49) 1
is the highest priority. A value of two (US-ASCII decimal 50) 2 is the second highest
priority. Subsequent numbers specify a decreasing ordinal
priority. A value of nine (US-ASCII decimal 57 ) 9 is the lowest priority.

A CUA with a three-level priority scheme of "HIGH", "MEDIUM" "MEDIUM", and
"LOW" is mapped into this property such that a property value in
the range of one (US-ASCII decimal 49) 1 to four (US-ASCII decimal
52) 4 specifies "HIGH" priority. A value of five (US-ASCII decimal
53) 5 is
the normal or "MEDIUM" priority. A value in the range of
six (US-ASCII decimal 54) 6 to nine (US-ASCII decimal 57 ) 9
is "LOW" priority.

A CUA with a priority schema of "A1", "A2", "A3", "B1", "B2", ...,
"C3" is mapped into this property such that a property value of
one (US-ASCII decimal 49) 1
specifies "A1", a property value of two
(US-ASCII decimal 50) 2 specifies "A2", a property
value of three
(US-ASCII decimal 51) 3 specifies "A3", and so forth up to a property value of
9 (US-ASCII decimal 57 ) specifies "C3".

Other integer values are reserved for future use.

Within a "VEVENT" calendar component, this property specifies a
priority for the event. This property may be useful when more
than one event is scheduled for a given time period.

Within a "VTODO" calendar component, this property specified a
priority for the to-do. This property is useful in prioritizing
multiple action items for a given time period.

Format Definition: This property is defined by the following
notation:

priority = "PRIORITY" prioparam ":" priovalue CRLF
;Default is zero (i.e., undefined) undefined).

prioparam = *(";" other-param)

priovalue = integer ;Must be in the range [0..9]
; All other values are reserved for future use use.

Example: The following is an example of a property with the highest
priority:

PRIORITY:1
The following is an example of a property with a next highest
priority:

PRIORITY:2

The following is an example of a property with no priority. This
is equivalent to not specifying the "PRIORITY" property:

PRIORITY:0

3.8.1.10. Resources

Property Name: RESOURCES

Purpose: This property defines the equipment or resources
anticipated for an activity specified by a calendar component.

Value Type: TEXT

Property Parameters: IANA, non-standard, alternate text
representation
representation, and language property parameters can be specified
on this property.

Conformance: This property can be specified once in "VEVENT" or
"VTODO" calendar component.

Description: The property value is an arbitrary text. More than one
resource can be specified as a COMMA-separated list of resources separated by the
COMMA character (US-ASCII decimal 44). resources.

Format Definition: This property is defined by the following
notation:

resources = "RESOURCES" resrcparam ":" text *("," text) CRLF

resrcparam = *(
;
; the The following are OPTIONAL,
; but MUST NOT occur more than once once.
;
(";" altrepparam) / (";" languageparam) /
;
; the The following is OPTIONAL,
; and MAY occur more than once once.
;
(";" other-param)
;
)
Example: The following is an example of this property:

RESOURCES:EASEL,PROJECTOR,VCR

RESOURCES;LANGUAGE=fr:Nettoyeur haute pression

3.8.1.11. Status

Property Name: STATUS

Purpose: This property defines the overall status or confirmation
for the calendar component.

Value Type: TEXT

Property Parameters: IANA and non-standard property parameters can
be specified on this property.

Conformance: This property can be specified once in "VEVENT",
"VTODO"
"VTODO", or "VJOURNAL" calendar components.

Description: In a group scheduled group-scheduled calendar component, the property
is used by the "Organizer" to provide a confirmation of the event
to the "Attendees". For example in a "VEVENT" calendar component,
the "Organizer" can indicate that a meeting is tentative,
confirmed
confirmed, or cancelled. In a "VTODO" calendar component, the
"Organizer" can indicate that an action item needs action, is
completed, is in process or being worked on, or has been
cancelled. In a "VJOURNAL" calendar component, the "Organizer"
can indicate that a journal entry is draft, final final, or has been
cancelled or removed.

Format Definition: This property is defined by the following
notation:

status = "STATUS" statparam ":" statvalue CRLF

statparam = *(";" other-param)

statvalue = (statvalue-event
/ statvalue-todo
/ statvalue-jour)

statvalue-event = "TENTATIVE" ;Indicates event is tentative.
/ "CONFIRMED" ;Indicates event is definite.
/ "CANCELLED" ;Indicates event was cancelled.
;Status values for a "VEVENT"

statvalue-todo = "NEEDS-ACTION" ;Indicates to-do needs action.
/ "COMPLETED" ;Indicates to-do completed.
/ "IN-PROCESS" ;Indicates to-do in process of.
/ "CANCELLED" ;Indicates to-do was cancelled.
;Status values for "VTODO".

statvalue-jour = "DRAFT" ;Indicates journal is draft.
/ "FINAL" ;Indicates journal is final.
/ "CANCELLED" ;Indicates journal is removed.
;Status values for "VJOURNAL".

Example: The following is an example of this property for a "VEVENT"
calendar component:

STATUS:TENTATIVE

The following is an example of this property for a "VTODO"
calendar component:

STATUS:NEEDS-ACTION

The following is an example of this property for a "VJOURNAL"
calendar component:

STATUS:DRAFT

3.8.1.12. Summary

Property Name: SUMMARY

Purpose: This property defines a short summary or subject for the
calendar component.

Value Type: TEXT

Property Parameters: IANA, non-standard, alternate text
representation
representation, and language property parameters can be specified
on this property.

Conformance: The property can be specified in "VEVENT", "VTODO",
"VJOURNAL"
"VJOURNAL", or "VALARM" calendar components.

Description: This property is used in the "VEVENT", "VTODO" "VTODO", and
"VJOURNAL" calendar components to capture a short, one line one-line
summary about the activity or journal entry.

This property is used in the "VALARM" calendar component to
capture the subject of an EMAIL category of alarm.

Format Definition: This property is defined by the following
notation:

summary = "SUMMARY" summparam ":" text CRLF

summparam = *(
;
; the The following are OPTIONAL,
; but MUST NOT occur more than once once.
;
(";" altrepparam) / (";" languageparam) /
;
; the The following is OPTIONAL,
; and MAY occur more than once once.
;
(";" other-param)
;
)

Example: The following is an example of this property:

SUMMARY:Department Party

3.8.2. Date and Time Component Properties

The following properties specify date and time related information in
calendar components.

3.8.2.1. Date/Time Date-Time Completed
Property Name: COMPLETED

Purpose: This property defines the date and time that a to-do was
actually completed.

Value Type: DATE-TIME

Property Parameters: IANA and non-standard property parameters can
be specified on this property.

Conformance: The property can be specified in a "VTODO" calendar
component. The value MUST be specified as a date with UTC time.

Description: This property defines the date and time that a to-do
was actually completed.

Format Definition: This property is defined by the following
notation:

completed = "COMPLETED" compparam ":" date-time CRLF

compparam = *(";" other-param)

Example: The following is an example of this property:

COMPLETED:19960401T150000Z

3.8.2.2. Date/Time Date-Time End

Property Name: DTEND

Purpose: This property specifies the date and time that a calendar
component ends.

Value Type: The default value type is DATE-TIME. The value type can
be set to a DATE value type.

Property Parameters: IANA, non-standard, value data type, and time
zone identifier property parameters can be specified on this
property.

Conformance: This property can be specified in "VEVENT" or
"VFREEBUSY" calendar components.

Description: Within the "VEVENT" calendar component, this property
defines the date and time by which the event ends. The value type
of this property MUST be the same as the "DTSTART" property, and
its value MUST be later in time than the value of the "DTSTART"
property. Furthermore, this property MUST be specified as a date
with local time if and only if the "DTSTART" property is also
specified as a date with local time.

Within the "VFREEBUSY" calendar component, this property defines
the end date and time for the free or busy time information. The
time MUST be specified in the UTC time format. The value MUST be
later in time than the value of the "DTSTART" property.

Format Definition: This property is defined by the following
notation:

dtend = "DTEND" dtendparam ":" dtendval CRLF

dtendparam = *(
;
; the The following are OPTIONAL,
; but MUST NOT occur more than once once.
;
(";" "VALUE" "=" ("DATE-TIME" / "DATE")) /
(";" tzidparam) /
;
; the The following is OPTIONAL,
; and MAY occur more than once once.
;
(";" other-param)
;
)

dtendval = date-time / date
;Value MUST match value type

Example: The following is an example of this property:

DTEND:19960401T150000Z

DTEND;VALUE=DATE:19980704

3.8.2.3. Date/Time Date-Time Due

Property Name: DUE

Purpose: This property defines the date and time that a to-do is
expected to be completed.

Value Type: The default value type is DATE-TIME. The value type can
be set to a DATE value type.

Property Parameters: IANA, non-standard, value data type, and time
zone identifier property parameters can be specified on this
property.

Conformance: The property can be specified once in a "VTODO"
calendar component.

Description: This property defines the date and time before which a
to-do is expected to be completed. For cases where this property
is specified in a "VTODO" calendar component that also specifies a
"DTSTART" property, the value type of this property MUST be the
same as the "DTSTART" property, and the value of this property
MUST be later in time than the value of the "DTSTART" property.
Furthermore, this property MUST be specified as a date with local
time if and only if the "DTSTART" property is also specified as a
date with local time.

Format Definition: This property is defined by the following
notation:

due = "DUE" dueparam ":" dueval CRLF

dueparam = *(
;
; the The following are OPTIONAL,
; but MUST NOT occur more than once once.
;
(";" "VALUE" "=" ("DATE-TIME" / "DATE")) /
(";" tzidparam) /
;
; the The following is OPTIONAL,
; and MAY occur more than once once.
;
(";" other-param)
;
)

dueval = date-time / date
;Value MUST match value type

Example: The following is an example of this property:

DUE:19980430T000000Z

3.8.2.4. Date/Time Date-Time Start

Property Name: DTSTART

Purpose: This property specifies when the calendar component begins.

Value Type: The default value type is DATE-TIME. The time value
MUST be one of the forms defined for the DATE-TIME value type.
The value type can be set to a DATE value type.

Property Parameters: IANA, non-standard, value data type, and time
zone identifier property parameters can be specified on this
property.

Conformance: This property can be specified once in the "VEVENT",
"VTODO", or "VFREEBUSY" calendar components as well as in the
"STANDARD" and "DAYLIGHT" sub-components. This property is
REQUIRED in all types of recurring calendar components that
specify the "RRULE" property. This property is also REQUIRED in
"VEVENT" calendar components contained in iCalendar objects that
don't specify the "METHOD" property.

Description: Within the "VEVENT" calendar component, this property
defines the start date and time for the event.

Within the "VFREEBUSY" calendar component, this property defines
the start date and time for the free or busy time information.
The time MUST be specified in UTC time.

Within the "STANDARD" and "DAYLIGHT" sub-components, this property
defines the effective start date and time for a time zone
specification. This property is REQUIRED within each "STANDARD"
and "DAYLIGHT" sub-components included in "VTIMEZONE" calendar
components and MUST be specified as a date with local time without
the "TZID" property parameter.

Format Definition: This property is defined by the following
notation:

dtstart = "DTSTART" dtstparam ":" dtstval CRLF

dtstparam = *(
;
; the The following are OPTIONAL,
; but MUST NOT occur more than once once.
;
(";" "VALUE" "=" ("DATE-TIME" / "DATE")) /
(";" tzidparam) /
;
; the The following is OPTIONAL,
; and MAY occur more than once once.
;
(";" other-param)
;
)

dtstval = date-time / date
;Value MUST match value type

Example: The following is an example of this property:

DTSTART:19980118T073000Z

3.8.2.5. Duration

Property Name: DURATION

Purpose: This property specifies a positive duration of time.

Value Type: DURATION

Property Parameters: IANA and non-standard property parameters can
be specified on this property.

Conformance: This property can be specified in "VEVENT", "VTODO", or
"VALARM" calendar components.

Description: In a "VEVENT" calendar component the property may be
used to specify a duration of the event, instead of an explicit
end date/time. DATE-TIME. In a "VTODO" calendar component the property may
be used to specify a duration for the to-do, instead of an
explicit due date/time. DATE-TIME. In a "VALARM" calendar component the
property may be used to specify the delay period prior to
repeating an alarm. When the "DURATION" property relates to a
"DTSTART" property that is specified as a DATE value, then the
"DURATION" property MUST be specified as a "dur-day" or "dur-week"
value.

Format Definition: This property is defined by the following
notation:

duration = "DURATION" durparam ":" dur-value CRLF
;consisting of a positive duration of time.

durparam = *(";" other-param)

Example: The following is an example of this property that specifies
an interval of time of 1 one hour and zero minutes and zero seconds:

DURATION:PT1H0M0S

The following is an example of this property that specifies an
interval of time of 15 minutes.

DURATION:PT15M

3.8.2.6. Free/Busy Time

Property Name: FREEBUSY

Purpose: This property defines one or more free or busy time
intervals.

Value Type: PERIOD

Property Parameters: IANA, non-standard, and free/busy time type
property parameters can be specified on this property.

Conformance: The property can be specified in a "VFREEBUSY" calendar
component.

Description: These time periods can be specified as either a start
and end date-time DATE-TIME or a start date-time DATE-TIME and duration. DURATION. The date and
time MUST be a UTC time format.

"FREEBUSY" properties within the "VFREEBUSY" calendar component
SHOULD be sorted in ascending order, based on start time and then
end time, with the earliest periods first.

The "FREEBUSY" property can specify more than one value, separated
by the COMMA character (US-ASCII decimal 44). character. In such cases, the "FREEBUSY" property
values MUST all be of the same "FBTYPE" property parameter type
(e.g., all values of a particular "FBTYPE" listed together in a
single property).

Format Definition: This property is defined by the following
notation:

freebusy = "FREEBUSY" fbparam ":" fbvalue CRLF

fbparam = *(
;
; the The following is OPTIONAL,
; but MUST NOT occur more than once once.
;
(";" fbtypeparam) /
;
; the The following is OPTIONAL,
; and MAY occur more than once once.
;
(";" other-param)
;
)

fbvalue = period *("," period)
;Time value MUST be in the UTC time format.

Example: The following are some examples of this property:

FREEBUSY;FBTYPE=BUSY-UNAVAILABLE:19970308T160000Z/PT8H30M

FREEBUSY;FBTYPE=FREE:19970308T160000Z/PT3H,19970308T200000Z/PT1H

FREEBUSY;FBTYPE=FREE:19970308T160000Z/PT3H,19970308T200000Z/PT1H
,19970308T230000Z/19970309T000000Z

3.8.2.7. Time Transparency

Property Name: TRANSP

Purpose: This property defines whether or not an event is
transparent or
not to busy time searches.

Value Type: TEXT

Property Parameters: IANA and non-standard property parameters can
be specified on this property.

Conformance: This property can be specified once in a "VEVENT"
calendar component.

Description: Time Transparency is the characteristic of an event
that determines whether it appears to consume time on a calendar.
Events that consume actual time for the individual or resource
associated with the calendar SHOULD be recorded as OPAQUE,
allowing them to be detected by free-busy free/busy time searches. Other
events, which do not take up the individual's (or resource's) time
SHOULD be recorded as TRANSPARENT, making them invisible to free- free/
busy time searches.

Format Definition: This property is defined by the following
notation:

transp = "TRANSP" transparam ":" transvalue CRLF

transparam = *(";" other-param)

transvalue = "OPAQUE"
;Blocks or opaque on busy time searches.
/ "TRANSPARENT"
;Transparent on busy time searches.
;Default value is OPAQUE

Example: The following is an example of this property for an event
that is transparent or does not block on free/busy time searches:

TRANSP:TRANSPARENT

The following is an example of this property for an event that is
opaque or blocks on free/busy time searches:

TRANSP:OPAQUE

3.8.3. Time Zone Component Properties

The following properties specify time zone information in calendar
components.

3.8.3.1. Time Zone Identifier

Property Name: TZID

Purpose: This property specifies the text value that uniquely
identifies the "VTIMEZONE" calendar component in the scope of an
iCalendar object.

Value Type: TEXT

Property Parameters: IANA and non-standard property parameters can
be specified on this property.

Conformance: This property MUST be specified in a "VTIMEZONE"
calendar component.

Description: This is the label by which a time zone calendar
component is referenced by any iCalendar properties whose value
type is either DATE-TIME or TIME and not intended to specify a UTC
or a "floating" time. The presence of the SOLIDUS character (US-
ASCII decimal 47) as a
prefix, indicates that this "TZID" represents an unique ID in a
globally defined time zone registry (when such registry is
defined).

Format Definition: This property is defined by the following
notation:

tzid = "TZID" tzidpropparam ":" [tzidprefix] text CRLF

tzidpropparam = *(";" other-param)

;tzidprefix = "/"
; Defined previously. Just listed here for reader convenience.

Example: The following are examples of non-globally unique time zone
identifiers:

TZID:America/New_York

TZID:America/Los_Angeles

The following is an example of a fictitious globally unique time
zone identifier:

TZID:/example.org/America/New_York

3.8.3.2. Time Zone Name

Property Name: TZNAME

Purpose: This property specifies the customary designation for a
time zone description.

Value Type: TEXT

Property Parameters: IANA, non-standard, and language property
parameters can be specified on this property.

Conformance: This property can be specified in "STANDARD" and
"DAYLIGHT" sub-components.

Description: This property specifies a customary name that can be
used when displaying dates that occur during the observance
defined by the time zone sub-component.

Format Definition: This property is defined by the following
notation:

tzname = "TZNAME" tznparam ":" text CRLF

tznparam = *(
;
; the The following is OPTIONAL,
; but MUST NOT occur more than once once.
;
(";" languageparam) /
;
; the The following is OPTIONAL,
; and MAY occur more than once once.
;
(";" other-param)
;
)

Example: The following are examples of this property:

TZNAME:EST

TZNAME;LANGUAGE=fr-CA:HNE

3.8.3.3. Time Zone Offset From

Property Name: TZOFFSETFROM

Purpose: This property specifies the offset which that is in use prior to
this time zone observance.

Value Type: UTC-OFFSET

Property Parameters: IANA and non-standard property parameters can
be specified on this property.

Conformance: This property MUST be specified in "STANDARD" and
"DAYLIGHT" sub-components.

Description: This property specifies the offset which that is in use prior
to this time observance. It is used to calculate the absolute
time at which the transition to a given observance takes place.
This property MUST only be specified in a "VTIMEZONE" calendar
component. A "VTIMEZONE" calendar component MUST include this
property. The property value is a signed numeric indicating the
number of hours and possibly minutes from UTC. Positive numbers
represent time zones east of the prime meridian, or ahead of UTC.
Negative numbers represent time zones west of the prime meridian,
or behind UTC.

Format Definition: This property is defined by the following
notation:

tzoffsetfrom = "TZOFFSETFROM" frmparam ":" utc-offset
CRLF

frmparam = *(";" other-param)

Example: The following are examples of this property:

TZOFFSETFROM:-0500

TZOFFSETFROM:+1345

3.8.3.4. Time Zone Offset To

Property Name: TZOFFSETTO

Purpose: This property specifies the offset which that is in use in this
time zone observance.

Value Type: UTC-OFFSET

Property Parameters: IANA and non-standard property parameters can
be specified on this property.

Conformance: This property MUST be specified in "STANDARD" and
"DAYLIGHT" sub-components.

Description: This property specifies the offset which that is in use in
this time zone observance. It is used to calculate the absolute
time for the new observance. The property value is a signed
numeric indicating the number of hours and possibly minutes from
UTC. Positive numbers represent time zones east of the prime
meridian, or ahead of UTC. Negative numbers represent time zones
west of the prime meridian, or behind UTC.

Format Definition: This property is defined by the following
notation:

tzoffsetto = "TZOFFSETTO" toparam ":" utc-offset CRLF

toparam = *(";" other-param)

Example: The following are examples of this property:

TZOFFSETTO:-0400

TZOFFSETTO:+1245

3.8.3.5. Time Zone URL

Property Name: TZURL

Purpose: This property provides a means for a "VTIMEZONE" component
to point to a network location that can be used to retrieve an up-
to-date version of itself.

Value Type: URI

Property Parameters: IANA and non-standard property parameters can
be specified on this property.

Conformance: This property can be specified in a "VTIMEZONE"
calendar component.

Description: This property provides a means for a "VTIMEZONE"
component to point to a network location that can be used to
retrieve an up-to-date version of itself. This provides a hook to
handle changes government bodies impose upon time zone
definitions. Retrieval of this resource results in an iCalendar
object containing a single "VTIMEZONE" component and a "METHOD"
property set to PUBLISH.

Format Definition: This property is defined by the following
notation:

tzurl = "TZURL" tzurlparam ":" uri CRLF

tzurlparam = *(";" other-param)

Example: The following is an example of this property:

TZURL:http://timezones.example.org/tz/America-Los_Angeles.ics

3.8.4. Relationship Component Properties

The following properties specify relationship information in calendar
components.

3.8.4.1. Attendee

Property Name: ATTENDEE

Purpose: This property defines an "Attendee" within a calendar
component.

Value Type: CAL-ADDRESS

Property Parameters: IANA, non-standard, language, calendar user
type, group or list membership, participation role, participation
status, RSVP expectation, delegatee, delegator, sent by, common
name
name, or directory entry reference property parameters can be
specified on this property.

Conformance: This property MUST be specified in an iCalendar object
that specifies a group scheduled group-scheduled calendar entity. This property
MUST NOT be specified in an iCalendar object when publishing the
calendar information (e.g., NOT in an iCalendar object that
specifies the publication of a calendar user's busy time, event,
to-do
to-do, or journal). This property is not specified in an
iCalendar object that specifies only a time zone definition or
that defines calendar components that are not group scheduled group-scheduled
components, but are components only on a single user's calendar.

Description: This property MUST only be specified within calendar
components to specify participants, non-participants non-participants, and the
chair of a group scheduled group-scheduled calendar entity. The property is
specified within an "EMAIL" category of the "VALARM" calendar
component to specify an email address that is to receive the email
type of iCalendar alarm.

The property parameter "CN" is for the common or displayable name
associated with the calendar address; "ROLE", for the intended
role that the attendee will have in the calendar component;
"PARTSTAT", for the status of the attendee's participation;
"RSVP", for indicating whether the favor of a reply is requested;
"CUTYPE", to indicate the type of calendar user; "MEMBER", to
indicate the groups that the attendee belongs to; "DELEGATED-TO",
to indicate the calendar users that the original request was
delegated to; and "DELEGATED-FROM", to indicate whom the request
was delegated from; "SENT-BY", to indicate whom is acting on
behalf of the "ATTENDEE"; and "DIR", to indicate the URI that
points to the directory information corresponding to the attendee.
These property parameters can be specified on an "ATTENDEE"
property in either a "VEVENT", "VTODO" "VTODO", or "VJOURNAL" calendar
component. They MUST NOT be specified in an "ATTENDEE" property
in a "VFREEBUSY" or "VALARM" calendar component. If the
"LANGUAGE" property parameter is specified, the identified
language applies to the "CN" parameter.

A recipient delegated a request MUST inherit the "RSVP" and "ROLE"
values from the attendee that delegated the request to them.

Multiple attendees can be specified by including multiple
"ATTENDEE" properties within the calendar component.

Format Definition: This property is defined by the following
notation:

attendee = "ATTENDEE" attparam ":" cal-address CRLF

attparam = *(
;
; the The following are OPTIONAL,
; but MUST NOT occur more than once once.
;
(";" cutypeparam) / (";" memberparam) /
(";" roleparam) / (";" partstatparam) /
(";" rsvpparam) / (";" deltoparam) /
(";" delfromparam) / (";" sentbyparam) /
(";" cnparam) / (";" dirparam) /
(";" languageparam) /
;
; the The following is OPTIONAL,
; and MAY occur more than once once.
;
(";" other-param)
;
)

Example: The following are examples of this property's use for a
to-do:

ATTENDEE;MEMBER="mailto:DEV-GROUP@example.com":
mailto:joecool@example.com
ATTENDEE;DELEGATED-FROM="mailto:immud@example.com":
mailto:ildoit@example.com

The following is an example of this property used for specifying
multiple attendees to an event:

ATTENDEE;ROLE=REQ-PARTICIPANT;PARTSTAT=TENTATIVE;CN=Henry
Cabot:mailto:hcabot@example.com
ATTENDEE;ROLE=REQ-PARTICIPANT;DELEGATED-FROM="mailto:bob@
example.com";PARTSTAT=ACCEPTED;CN=Jane Doe:mailto:jdoe@
example.com

The following is an example of this property with a URI to the
directory information associated with the attendee:

ATTENDEE;CN=John Smith;DIR="ldap://example.com:6666/o=ABC%
20Industries,c=US???(cn=Jim%20Dolittle)":mailto:jimdo@
example.com
The following is an example of this property with "delegatee" and
"delegator" information for an event:

ATTENDEE;ROLE=REQ-PARTICIPANT;PARTSTAT=TENTATIVE;DELEGATED-FROM=
"mailto:iamboss@example.com";CN=Henry Cabot:mailto:hcabot@
example.com
ATTENDEE;ROLE=NON-PARTICIPANT;PARTSTAT=DELEGATED;DELEGATED-TO=
"mailto:hcabot@example.com";CN=The Big Cheese:mailto:iamboss
@example.com
ATTENDEE;ROLE=REQ-PARTICIPANT;PARTSTAT=ACCEPTED;CN=Jane Doe
:mailto:jdoe@example.com

Example: The following is an example of this property's use when
another calendar user is acting on behalf of the "Attendee":

ATTENDEE;SENT-BY=mailto:jan_doe@example.com;CN=John Smith:
mailto:jsmith@example.com

3.8.4.2. Contact

Property Name: CONTACT

Purpose: This property is used to represent contact information or
alternately a reference to contact information associated with the
calendar component.

Value Type: TEXT

Property Parameters: IANA, non-standard, alternate text
representation
representation, and language property parameters can be specified
on this property.

Conformance: This property can be specified in a "VEVENT", "VTODO",
"VJOURNAL"
"VJOURNAL", or "VFREEBUSY" calendar component.

Description: The property value consists of textual contact
information. An alternative representation for the property value
can also be specified that refers to a URI pointing to an
alternate form, such as a vCard [RFC2426], for the contact
information.

Format Definition: This property is defined by the following
notation:

contact = "CONTACT" contparam ":" text CRLF

contparam = *(
;
; the The following are OPTIONAL,
; but MUST NOT occur more than once once.
;
(";" altrepparam) / (";" languageparam) /
;
; the The following is OPTIONAL,
; and MAY occur more than once once.
;
(";" other-param)
;
)

Example: The following is an example of this property referencing
textual contact information:

CONTACT:Jim Dolittle\, ABC Industries\, +1-919-555-1234

The following is an example of this property with an alternate
representation of a an LDAP URI to a directory entry containing the
contact information:

CONTACT;ALTREP="ldap://example.com:6666/o=ABC%20Industries\,
c=US???(cn=Jim%20Dolittle)":Jim Dolittle\, ABC Industries\,
+1-919-555-1234

The following is an example of this property with an alternate
representation of a MIME body part containing the contact
information, such as a vCard [RFC2426] embedded in a text/
directory media type [RFC2425]:

CONTACT;ALTREP="CID:part3.msg970930T083000SILVER@example.com":
Jim Dolittle\, ABC Industries\, +1-919-555-1234

The following is an example of this property referencing a network
resource, such as a vCard [RFC2426] object containing the contact
information:

CONTACT;ALTREP="http://example.com/pdi/jdoe.vcf":Jim
Dolittle\, ABC Industries\, +1-919-555-1234

3.8.4.3. Organizer

Property Name: ORGANIZER

Purpose: This property defines the organizer for a calendar
component.

Value Type: CAL-ADDRESS

Property Parameters: IANA, non-standard, language, common name,
directory entry reference, sent by and sent-by property parameters can be
specified on this property.

Conformance: This property MUST be specified in an iCalendar object
that specifies a group scheduled group-scheduled calendar entity. This property
MUST be specified in an iCalendar object that specifies the
publication of a calendar user's busy time. This property MUST
NOT be specified in an iCalendar object that specifies only a time
zone definition or that defines calendar components that are not
group scheduled
group-scheduled components, but are components only on a single
user's calendar.

Description: This property is specified within the "VEVENT",
"VTODO", and "VJOURNAL" calendar components to specify the
organizer of a group scheduled group-scheduled calendar entity. The property is
specified within the "VFREEBUSY" calendar component to specify the
calendar user requesting the free or busy time. When publishing a
"VFREEBUSY" calendar component, the property is used to specify
the calendar that the published busy time came from.

The property has the property parameters "CN", for specifying the
common or display name associated with the "Organizer", "DIR", for
specifying a pointer to the directory information associated with
the "Organizer", "SENT-BY", for specifying another calendar user
that is acting on behalf of the "Organizer". The non-standard
parameters may also be specified on this property. If the
"LANGUAGE" property parameter is specified, the identified
language applies to the "CN" parameter value.

Format Definition: This property is defined by the following
notation:

organizer = "ORGANIZER" orgparam ":"
cal-address CRLF

orgparam = *(
;
; the The following are OPTIONAL,
; but MUST NOT occur more than once once.
;
(";" cnparam) / (";" dirparam) / (";" sentbyparam) /
(";" languageparam) /
;
; the The following is OPTIONAL,
; and MAY occur more than once once.
;
(";" other-param)
;
)

Example: The following is an example of this property:

ORGANIZER;CN=John Smith:mailto:jsmith@example.com

The following is an example of this property with a pointer to the
directory information associated with the organizer:

ORGANIZER;CN=JohnSmith;DIR="ldap://example.com:6666/o=DC%20Ass
ociates,c=US???(cn=John%20Smith)":mailto:jsmith@example.com

The following is an example of this property used by another
calendar user who is acting on behalf of the organizer, with
responses intended to be sent back to the organizer, not the other
calendar user:

ORGANIZER;SENT-BY="mailto:jane_doe@example.com":
mailto:jsmith@example.com

3.8.4.4. Recurrence ID

Property Name: RECURRENCE-ID

Purpose: This property is used in conjunction with the "UID" and
"SEQUENCE" property properties to identify a specific instance of a
recurring "VEVENT", "VTODO" "VTODO", or "VJOURNAL" calendar component.
The property value is the original value of the "DTSTART" property
of the recurrence instance.

Value Type: The default value type for this property is DATE-TIME.
The default value type is DATE-TIME. The value type can
be set to a DATE value type. This property MUST have the same
value type as the "DTSTART" property contained within the
recurring component. Furthermore, this property MUST be specified
as a date with local time if and only if the "DTSTART" property
contained within the recurring component is specified as a date
with local time.

Property Parameters: IANA, non-standard, value data type, time zone
identifier
identifier, and recurrence identifier range parameters can be
specified on this property.

Conformance: This property can be specified in an iCalendar object
containing a recurring calendar component.

Description: The full range of calendar components specified by a
recurrence set is referenced by referring to just the "UID"
property value corresponding to the calendar component. The
"RECURRENCE-ID" property allows the reference to an individual
instance within the recurrence set.

If the value of the "DTSTART" property is a DATE type value, then
the value MUST be the calendar date for the recurrence instance.

The DATE-TIME value is set to the time when the original
recurrence instance would occur; meaning that if the intent is to
change a Friday meeting to Thursday, the DATE-TIME is still set to
the original Friday meeting.

The "RECURRENCE-ID" property is used in conjunction with the "UID"
and "SEQUENCE" property properties to identify a particular instance of a
recurring event, to-do to-do, or journal. For a given pair of "UID" and
"SEQUENCE" property values, the "RECURRENCE-ID" value for a
recurrence instance is fixed.

The "RANGE" parameter is used to specify the effective range of
recurrence instances from the instance specified by the
"RECURRENCE-ID" property value. The value for the range parameter
can only be "THISANDFUTURE" to indicate a range defined by the
given recurrence instance and all subsequent instances.
Subsequent instances are determined by their "RECURRENCE-ID" value
and not their current scheduled start time. Subsequent instances
defined in separate components are not impacted by the given
recurrence instance. When the given recurrence instance is
rescheduled, all subsequent instances are also rescheduled by the
same time difference. For instance, if the given recurrence
instance is rescheduled to start 2 hours later, then all
subsequent instances are also rescheduled 2 hours later.

Similarly, if the duration of the given recurrence instance is
modified, then all subsequence instances are also modified to have
this same duration.

Note: The "RANGE" parameter may not be appropriate to
reschedule specific subsequent instances of complex recurring
calendar component. Assuming an unbounded recurring calendar
component scheduled to occur on Mondays and Wednesdays, the
"RANGE" parameter could not be used to reschedule only the
future Monday instances to occur on Tuesday instead. In such
cases, the calendar application could simply truncate the
unbounded recurring calendar component (i.e., with the "COUNT"
or "UNTIL" rule parts), and create two new unbounded recurring
calendar components for the future instances.

Format Definition: This property is defined by the following
notation:

recurid = "RECURRENCE-ID" ridparam ":" ridval CRLF

ridparam = *(
;
; the The following are OPTIONAL,
; but MUST NOT occur more than once once.
;
(";" "VALUE" "=" ("DATE-TIME" / "DATE")) /
(";" tzidparam) / (";" rangeparam) /
;
; the The following is OPTIONAL,
; and MAY occur more than once once.
;
(";" other-param)
;
)

ridval = date-time / date
;Value MUST match value type

Example: The following are examples of this property:

RECURRENCE-ID;VALUE=DATE:19960401

RECURRENCE-ID;RANGE=THISANDFUTURE:19960120T120000Z

3.8.4.5. Related To

Property Name: RELATED-TO

Purpose: This property is used to represent a relationship or
reference between one calendar component and another.

Value Type: TEXT

Property Parameters: IANA, non-standard, and relationship type
property parameters can be specified on this property.

Conformance: This property can be specified in the "VEVENT", "VTODO"
"VTODO", and "VJOURNAL" calendar components.

Description: The property value consists of the persistent, globally
unique identifier of another calendar component. This value would
be represented in a calendar component by the "UID" property.

By default, the property value points to another calendar
component that has a PARENT relationship to the referencing
object. The "RELTYPE" property parameter is used to either
explicitly state the default PARENT relationship type to the
referenced calendar component or to override the default PARENT
relationship type and specify either a CHILD or SIBLING
relationship. The PARENT relationship indicates that the calendar
component is a subordinate of the referenced calendar component.
The CHILD relationship indicates that the calendar component is a
superior of the referenced calendar component. The SIBLING
relationship indicates that the calendar component is a peer of
the referenced calendar component.

Changes to a calendar component referenced by this property can
have an implicit impact on the related calendar component. For
example, if a group event changes its start or end date or time,
then the related, dependent events will need to have their start
and end dates changed in a corresponding way. Similarly, if a
PARENT calendar component is cancelled or deleted, then there is
an implied impact to the related CHILD calendar components. This
property is intended only to provide information on the
relationship of calendar components. It is up to the target
calendar system to maintain any property implications of this
relationship.

Format Definition: This property is defined by the following
notation:

related = "RELATED-TO" relparam ":" text CRLF

relparam = *(
;
; the The following is OPTIONAL,
; but MUST NOT occur more than once once.
;
(";" reltypeparam) /
;
; the The following is OPTIONAL,
; and MAY occur more than once once.
;
(";" other-param)
;
)

The following is an example of this property:

RELATED-TO:jsmith.part7.19960817T083000.xyzMail@example.com

RELATED-TO:19960401-080045-4000F192713-0052@example.com

3.8.4.6. Uniform Resource Locator

Property Name: URL

Purpose: This property defines a Uniform Resource Locator (URL)
associated with the iCalendar object.

Value Type: URI

Property Parameters: IANA and non-standard property parameters can
be specified on this property.

Conformance: This property can be specified once in the "VEVENT",
"VTODO", "VJOURNAL" "VJOURNAL", or "VFREEBUSY" calendar components.

Description: This property may be used in a calendar component to
convey a location where a more dynamic rendition of the calendar
information associated with the calendar component can be found.
This memo does not attempt to standardize the form of the URI, nor
the format of the resource pointed to by the property value. If
the URL property and Content-Location MIME header are both
specified, they MUST point to the same resource.

Format Definition: This property is defined by the following
notation:

url = "URL" urlparam ":" uri CRLF

urlparam = *(";" other-param)

Example: The following is an example of this property:

URL:http://example.com/pub/calendars/jsmith/mytime.ics

3.8.4.7. Unique Identifier

Property Name: UID

Purpose: This property defines the persistent, globally unique
identifier for the calendar component.

Value Type: TEXT

Property Parameters: IANA and non-standard property parameters can
be specified on this property.

Conformance: The property MUST be specified in the "VEVENT",
"VTODO", "VJOURNAL" "VJOURNAL", or "VFREEBUSY" calendar components.

Description: The "UID" itself MUST be a globally unique identifier.
The generator of the identifier MUST guarantee that the identifier
is unique. There are several algorithms that can be used to
accomplish this. A good method to assure uniqueness is to put the
domain name or a domain literal IP address of the host on which
the identifier was created on the right hand right-hand side of an "@", and
on the left hand left-hand side, put a combination of the current calendar
date and time of day (i.e., formatted in as a DATE-TIME value)
along with some other currently unique (perhaps sequential)
identifier available on the system (for example, a process id
number). Using a date/time DATE-TIME value on the left hand left-hand side and a
domain name or domain literal on the right hand right-hand side makes it
possible to guarantee uniqueness since no two hosts should be
using the same domain name or IP address at the same time. Though
other algorithms will work, it is RECOMMENDED that the right hand right-hand
side contain some domain identifier (either of the host itself or
otherwise) such that the generator of the message identifier can
guarantee the uniqueness of the left hand left-hand side within the scope of
that domain.

This is the method for correlating scheduling messages with the
referenced "VEVENT", "VTODO", or "VJOURNAL" calendar component.

The full range of calendar components specified by a recurrence
set is referenced by referring to just the "UID" property value
corresponding to the calendar component. The "RECURRENCE-ID"
property allows the reference to an individual instance within the
recurrence set.

This property is an important method for group scheduling group-scheduling
applications to match requests with later replies, modifications modifications,
or deletion requests. Calendaring and scheduling applications
MUST generate this property in "VEVENT", "VTODO" "VTODO", and "VJOURNAL"
calendar components to assure interoperability with other group group-
scheduling applications. This identifier is created by the
calendar system that generates an iCalendar object.

Implementations MUST be able to receive and persist values of at
least 255 octets for this property property, but they MUST NOT truncate
values in the middle of a UTF-8 multi-octet sequence.

Format Definition: This property is defined by the following
notation:

uid = "UID" uidparam ":" text CRLF

uidparam = *(";" other-param)

Example: The following is an example of this property:

UID:19960401T080045Z-4000F192713-0052@example.com

3.8.5. Recurrence Component Properties

The following properties specify recurrence information in calendar
components.

3.8.5.1. Exception Date/Times Date-Times

Property Name: EXDATE

Purpose: This property defines the list of date/time DATE-TIME exceptions for
recurring events, to-dos, journal entries entries, or time zone
definitions.

Value Type: The default value type for this property is DATE-TIME.
The value type can be set to DATE.

Property Parameters: IANA, non-standard, value data type type, and time
zone identifier property parameters can be specified on this
property.

Conformance: This property can be specified in recurring "VEVENT",
"VTODO", and "VJOURNAL" calendar components as well as in the
"STANDARD" and "DAYLIGHT" sub-components of the "VTIMEZONE"
calendar component.

Description: The exception dates, if specified, are used in
computing the recurrence set. The recurrence set is the complete
set of recurrence instances for a calendar component. The
recurrence set is generated by considering the initial "DTSTART"
property along with the "RRULE", "RDATE", and "EXDATE" properties
contained within the recurring component. The "DTSTART" property
defines the first instance in the recurrence set. The "DTSTART"
property value SHOULD match the pattern of the recurrence rule, if
specified. The recurrence set generated with a "DTSTART" property
value that doesn't match the pattern of the rule is undefined.
The final recurrence set is generated by gathering all of the
start date-times DATE-TIME values generated by any of the specified "RRULE"
and "RDATE" properties, and then excluding any start date and times DATE-TIME
values specified by "EXDATE" properties. This implies that start date
and times
DATE-TIME values specified by "EXDATE" properties take precedence
over those specified by inclusion properties (i.e., "RDATE" and
"RRULE"). When duplicate instances are generated by the "RRULE"
and "RDATE" properties, only one recurrence is considered.
Duplicate instances are ignored.

The "EXDATE" property can be used to exclude the value specified
in "DTSTART". However, in such cases cases, the original "DTSTART" date
MUST still be maintained by the calendaring and scheduling system
because the original "DTSTART" value has inherent usage
dependencies by other properties such as the "RECURRENCE-ID".

Format Definition: This property is defined by the following
notation:

exdate = "EXDATE" exdtparam ":" exdtval *("," exdtval) CRLF

exdtparam = *(
;
; the The following are OPTIONAL,
; but MUST NOT occur more than once once.
;
(";" "VALUE" "=" ("DATE-TIME" / "DATE")) /
;
(";" tzidparam) /
;
; the The following is OPTIONAL,
; and MAY occur more than once once.
;
(";" other-param)
;
)

exdtval = date-time / date
;Value MUST match value type

Example: The following is an example of this property:

EXDATE:19960402T010000Z,19960403T010000Z,19960404T010000Z

3.8.5.2. Recurrence Date/Times Date-Times

Property Name: RDATE

Purpose: This property defines the list of date/times DATE-TIME values for
recurring events, to-dos, journal entries entries, or time zone
definitions.

Value Type: The default value type for this property is DATE-TIME.
The value type can be set to DATE or PERIOD.

Property Parameters: IANA, non-standard, value data type type, and time
zone identifier property parameters can be specified on this
property.

Description: This property can appear along with the "RRULE"
property to define an aggregate set of repeating occurrences.
When they both appear in a recurring component, the recurrence
instances are defined by the union of occurrences defined by both
the "RDATE" and "RRULE".

The recurrence dates, if specified, are used in computing the
recurrence set. The recurrence set is the complete set of
recurrence instances for a calendar component. The recurrence set
is generated by considering the initial "DTSTART" property along
with the "RRULE", "RDATE", and "EXDATE" properties contained
within the recurring component. The "DTSTART" property defines
the first instance in the recurrence set. The "DTSTART" property
value SHOULD match the pattern of the recurrence rule, if
specified. The recurrence set generated with a "DTSTART" property
value that doesn't match the pattern of the rule is undefined.
The final recurrence set is generated by gathering all of the
start date-times DATE-TIME values generated by any of the specified "RRULE"
and "RDATE" properties, and then excluding any start date and times DATE-TIME
values specified by "EXDATE" properties. This implies that start date/
times
DATE-TIME values specified by "EXDATE" properties take precedence
over those specified by inclusion properties (i.e., "RDATE" and
"RRULE"). Where duplicate instances are generated by the "RRULE"
and "RDATE" properties, only one recurrence is considered.
Duplicate instances are ignored.

Format Definition: This property is defined by the following
notation:

rdate = "RDATE" rdtparam ":" rdtval *("," rdtval) CRLF

rdtparam = *(
;
; the The following are OPTIONAL,
; but MUST NOT occur more than once once.
;
(";" "VALUE" "=" ("DATE-TIME" / "DATE" / "PERIOD")) /
(";" tzidparam) /
;
; the The following is OPTIONAL,
; and MAY occur more than once once.
;
(";" other-param)
;
)

rdtval = date-time / date / period
;Value MUST match value type
Example: The following are examples of this property:

RDATE:19970714T123000Z
RDATE;TZID=America/New_York:19970714T083000

RDATE;VALUE=PERIOD:19960403T020000Z/19960403T040000Z,
19960404T010000Z/PT3H

RDATE;VALUE=DATE:19970101,19970120,19970217,19970421
19970526,19970704,19970901,19971014,19971128,19971129,19971225

3.8.5.3. Recurrence Rule

Property Name: RRULE

Purpose: This property defines a rule or repeating pattern for
recurring events, to-dos, journal entries entries, or time zone
definitions.

Value Type: RECUR

Property Parameters: IANA and non-standard property parameters can
be specified on this property.

Conformance: This property can be specified in recurring "VEVENT",
"VTODO"
"VTODO", and "VJOURNAL" calendar components as well as in the
"STANDARD" and "DAYLIGHT" sub-components of the "VTIMEZONE"
calendar component, but it SHOULD NOT be specified more than once.
The recurrence set generated with multiple "RRULE" properties is
undefined.

Description: The recurrence rule, if specified, is used in computing
the recurrence set. The recurrence set is the complete set of
recurrence instances for a calendar component. The recurrence set
is generated by considering the initial "DTSTART" property along
with the "RRULE", "RDATE", and "EXDATE" properties contained
within the recurring component. The "DTSTART" property defines
the first instance in the recurrence set. The "DTSTART" property
value SHOULD be synchronized with the recurrence rule, if
specified. The recurrence set generated with a "DTSTART" property
value not synchronized with the recurrence rule is undefined. The
final recurrence set is generated by gathering all of the start
date/times
DATE-TIME values generated by any of the specified "RRULE" and
"RDATE" properties, and then excluding any start date/times DATE-TIME values
specified by "EXDATE" properties. This implies that start date/times DATE-
TIME values specified by "EXDATE" properties take precedence over
those specified by inclusion properties (i.e., "RDATE" and
"RRULE"). Where duplicate instances are generated by the "RRULE"
and "RDATE" properties, only one recurrence is considered.
Duplicate instances are ignored.

The "DTSTART" property specified within the iCalendar object
defines the first instance of the recurrence. In most cases, a
"DTSTART" property of DATE-TIME value type used with a recurrence
rule, should be specified as a date with local time and time zone
reference to make sure all the recurrence instances start at the
same local time regardless of time zone changes.

If the duration of the recurring component is specified with the
"DTEND" or "DUE" property, then the same exact duration will apply
to all the members of the generated recurrence set. Else, if the
duration of the recurring component is specified with the
"DURATION" property, then the same nominal duration will apply to
all the members of the generated recurrence set and the exact
duration of each recurrence instance will depend on its specific
start time. For example, recurrence instances of a nominal
duration of one day will have an exact duration of more or less
than 24 hours on a day where a time zone shift occurs. The
duration of a specific recurrence may be modified in an exception
component or simply by using an "RDATE" property of PERIOD value
type.

Format Definition: This property is defined by the following
notation:

rrule = "RRULE" rrulparam ":" recur CRLF

rrulparam = *(";" other-param)

Example: All examples assume the Eastern United States time zone.

Daily for 10 occurrences:

DTSTART;TZID=America/New_York:19970902T090000
RRULE:FREQ=DAILY;COUNT=10

==> (1997 9:00 AM EDT) September 2-11

Daily until December 24, 1997:

DTSTART;TZID=America/New_York:19970902T090000
RRULE:FREQ=DAILY;UNTIL=19971224T000000Z

==> (1997 9:00 AM EDT) September 2-30;October 1-25
(1997 9:00 AM EST) October 26-31;November 1-30;December 1-23
Every other day - forever:

DTSTART;TZID=America/New_York:19970902T090000
RRULE:FREQ=DAILY;INTERVAL=2

==> (1997 9:00 AM EDT) September 2,4,6,8...24,26,28,30;
October 2,4,6...20,22,24
(1997 9:00 AM EST) October 26,28,30;
November 1,3,5,7...25,27,29;
December 1,3,...

Every 10 days, 5 occurrences:

DTSTART;TZID=America/New_York:19970902T090000
RRULE:FREQ=DAILY;INTERVAL=10;COUNT=5

==> (1997 9:00 AM EDT) September 2,12,22;
October 2,12

Everyday

Every day in January, for 3 years:

DTSTART;TZID=America/New_York:19980101T090000

RRULE:FREQ=YEARLY;UNTIL=20000131T140000Z;
BYMONTH=1;BYDAY=SU,MO,TU,WE,TH,FR,SA
or
RRULE:FREQ=DAILY;UNTIL=20000131T140000Z;BYMONTH=1

==> (1998 9:00 AM EST)January 1-31
(1999 9:00 AM EST)January 1-31
(2000 9:00 AM EST)January 1-31

Weekly for 10 occurrences occurrences:

DTSTART;TZID=America/New_York:19970902T090000
RRULE:FREQ=WEEKLY;COUNT=10

==> (1997 9:00 AM EDT) September 2,9,16,23,30;October 7,14,21
(1997 9:00 AM EST) October 28;November 4

Weekly until December 24, 1997 1997:

DTSTART;TZID=America/New_York:19970902T090000
RRULE:FREQ=WEEKLY;UNTIL=19971224T000000Z

==> (1997 9:00 AM EDT) September 2,9,16,23,30;
October 7,14,21
(1997 9:00 AM EST) October 28;
November 4,11,18,25;
December 2,9,16,23

Every other week - forever:

DTSTART;TZID=America/New_York:19970902T090000
RRULE:FREQ=WEEKLY;INTERVAL=2;WKST=SU

==> (1997 9:00 AM EDT) September 2,16,30;
October 14
(1997 9:00 AM EST) October 28;
November 11,25;
December 9,23
(1998 9:00 AM EST) January 6,20;
February 3, 17
...

Weekly on Tuesday and Thursday for 5 five weeks:

DTSTART;TZID=America/New_York:19970902T090000
RRULE:FREQ=WEEKLY;UNTIL=19971007T000000Z;WKST=SU;BYDAY=TU,TH

RRULE:FREQ=WEEKLY;COUNT=10;WKST=SU;BYDAY=TU,TH

==> (1997 9:00 AM EDT) September 2,4,9,11,16,18,23,25,30;
October 2

Every other week on Monday, Wednesday Wednesday, and Friday until December
24, 1997, starting on Monday, September 1, 1997:

DTSTART;TZID=America/New_York:19970901T090000
RRULE:FREQ=WEEKLY;INTERVAL=2;UNTIL=19971224T000000Z;WKST=SU;
BYDAY=MO,WE,FR

==> (1997 9:00 AM EDT) September 1,3,5,15,17,19,29;
October 1,3,13,15,17
(1997 9:00 AM EST) October 27,29,31;
November 10,12,14,24,26,28;
December 8,10,12,22
Every other week on Tuesday and Thursday, for 8 occurrences:

DTSTART;TZID=America/New_York:19970902T090000
RRULE:FREQ=WEEKLY;INTERVAL=2;COUNT=8;WKST=SU;BYDAY=TU,TH

==> (1997 9:00 AM EDT) September 2,4,16,18,30;
October 2,14,16

Monthly on the 1st first Friday for ten 10 occurrences:

DTSTART;TZID=America/New_York:19970905T090000
RRULE:FREQ=MONTHLY;COUNT=10;BYDAY=1FR

==> (1997 9:00 AM EDT) September 5;October 3
(1997 9:00 AM EST) November 7;December 5
(1998 9:00 AM EST) January 2;February 6;March 6;April 3
(1998 9:00 AM EDT) May 1;June 5

Monthly on the 1st first Friday until December 24, 1997:

DTSTART;TZID=America/New_York:19970905T090000
RRULE:FREQ=MONTHLY;UNTIL=19971224T000000Z;BYDAY=1FR

==> (1997 9:00 AM EDT) September 5; October 3
(1997 9:00 AM EST) November 7; December 5

Every other month on the 1st first and last Sunday of the month for 10
occurrences:

DTSTART;TZID=America/New_York:19970907T090000
RRULE:FREQ=MONTHLY;INTERVAL=2;COUNT=10;BYDAY=1SU,-1SU

==> (1997 9:00 AM EDT) September 7,28
(1997 9:00 AM EST) November 2,30
(1998 9:00 AM EST) January 4,25;March 1,29
(1998 9:00 AM EDT) May 3,31

Monthly on the second to last second-to-last Monday of the month for 6 months:

DTSTART;TZID=America/New_York:19970922T090000
RRULE:FREQ=MONTHLY;COUNT=6;BYDAY=-2MO

==> (1997 9:00 AM EDT) September 22;October 20
(1997 9:00 AM EST) November 17;December 22
(1998 9:00 AM EST) January 19;February 16
Monthly on the third to the last third-to-the-last day of the month, forever:

DTSTART;TZID=America/New_York:19970928T090000
RRULE:FREQ=MONTHLY;BYMONTHDAY=-3

==> (1997 9:00 AM EDT) September 28
(1997 9:00 AM EST) October 29;November 28;December 29
(1998 9:00 AM EST) January 29;February 26
...

Monthly on the 2nd and 15th of the month for 10 occurrences:

DTSTART;TZID=America/New_York:19970902T090000
RRULE:FREQ=MONTHLY;COUNT=10;BYMONTHDAY=2,15

==> (1997 9:00 AM EDT) September 2,15;October 2,15
(1997 9:00 AM EST) November 2,15;December 2,15
(1998 9:00 AM EST) January 2,15

Monthly on the first and last day of the month for 10 occurrences:

DTSTART;TZID=America/New_York:19970930T090000
RRULE:FREQ=MONTHLY;COUNT=10;BYMONTHDAY=1,-1

==> (1997 9:00 AM EDT) September 30;October 1
(1997 9:00 AM EST) October 31;November 1,30;December 1,31
(1998 9:00 AM EST) January 1,31;February 1

Every 18 months on the 10th thru 15th of the month for 10
occurrences:

DTSTART;TZID=America/New_York:19970910T090000
RRULE:FREQ=MONTHLY;INTERVAL=18;COUNT=10;BYMONTHDAY=10,11,12,
13,14,15

==> (1997 9:00 AM EDT) September 10,11,12,13,14,15
(1999 9:00 AM EST) March 10,11,12,13

Every Tuesday, every other month:

DTSTART;TZID=America/New_York:19970902T090000
RRULE:FREQ=MONTHLY;INTERVAL=2;BYDAY=TU

==> (1997 9:00 AM EDT) September 2,9,16,23,30
(1997 9:00 AM EST) November 4,11,18,25
(1998 9:00 AM EST) January 6,13,20,27;March 3,10,17,24,31
...

Yearly in June and July for 10 occurrences:

DTSTART;TZID=America/New_York:19970610T090000
RRULE:FREQ=YEARLY;COUNT=10;BYMONTH=6,7

==> (1997 9:00 AM EDT) June 10;July 10
(1998 9:00 AM EDT) June 10;July 10
(1999 9:00 AM EDT) June 10;July 10
(2000 9:00 AM EDT) June 10;July 10
(2001 9:00 AM EDT) June 10;July 10

Note: Since none of the BYDAY, BYMONTHDAY BYMONTHDAY, or BYYEARDAY
components are specified, the day is gotten from "DTSTART" "DTSTART".

Every other year on January, February, and March for 10
occurrences:

DTSTART;TZID=America/New_York:19970310T090000
RRULE:FREQ=YEARLY;INTERVAL=2;COUNT=10;BYMONTH=1,2,3

==> (1997 9:00 AM EST) March 10
(1999 9:00 AM EST) January 10;February 10;March 10
(2001 9:00 AM EST) January 10;February 10;March 10
(2003 9:00 AM EST) January 10;February 10;March 10

Every 3rd third year on the 1st, 100th 100th, and 200th day for 10
occurrences:

DTSTART;TZID=America/New_York:19970101T090000
RRULE:FREQ=YEARLY;INTERVAL=3;COUNT=10;BYYEARDAY=1,100,200

==> (1997 9:00 AM EST) January 1
(1997 9:00 AM EDT) April 10;July 19
(2000 9:00 AM EST) January 1
(2000 9:00 AM EDT) April 9;July 18
(2003 9:00 AM EST) January 1
(2003 9:00 AM EDT) April 10;July 19
(2006 9:00 AM EST) January 1

Every 20th Monday of the year, forever:

DTSTART;TZID=America/New_York:19970519T090000
RRULE:FREQ=YEARLY;BYDAY=20MO

==> (1997 9:00 AM EDT) May 19
(1998 9:00 AM EDT) May 18
(1999 9:00 AM EDT) May 17
...

Monday of week number 20 (where the default start of the week is
Monday), forever:

DTSTART;TZID=America/New_York:19970512T090000
RRULE:FREQ=YEARLY;BYWEEKNO=20;BYDAY=MO

==> (1997 9:00 AM EDT) May 12
(1998 9:00 AM EDT) May 11
(1999 9:00 AM EDT) May 17
...

Every Thursday in March, forever:

DTSTART;TZID=America/New_York:19970313T090000
RRULE:FREQ=YEARLY;BYMONTH=3;BYDAY=TH

==> (1997 9:00 AM EST) March 13,20,27
(1998 9:00 AM EST) March 5,12,19,26
(1999 9:00 AM EST) March 4,11,18,25
...

Every Thursday, but only during June, July, and August, forever:

DTSTART;TZID=America/New_York:19970605T090000
RRULE:FREQ=YEARLY;BYDAY=TH;BYMONTH=6,7,8

==> (1997 9:00 AM EDT) June 5,12,19,26;July 3,10,17,24,31;
August 7,14,21,28
(1998 9:00 AM EDT) June 4,11,18,25;July 2,9,16,23,30;
August 6,13,20,27
(1999 9:00 AM EDT) June 3,10,17,24;July 1,8,15,22,29;
August 5,12,19,26
...

Every Friday the 13th, forever:

DTSTART;TZID=America/New_York:19970902T090000
EXDATE;TZID=America/New_York:19970902T090000
RRULE:FREQ=MONTHLY;BYDAY=FR;BYMONTHDAY=13

==> (1998 9:00 AM EST) February 13;March 13;November 13
(1999 9:00 AM EDT) August 13
(2000 9:00 AM EDT) October 13
...

The first Saturday that follows the first Sunday of the month,
forever:

DTSTART;TZID=America/New_York:19970913T090000
RRULE:FREQ=MONTHLY;BYDAY=SA;BYMONTHDAY=7,8,9,10,11,12,13

==> (1997 9:00 AM EDT) September 13;October 11
(1997 9:00 AM EST) November 8;December 13
(1998 9:00 AM EST) January 10;February 7;March 7
(1998 9:00 AM EDT) April 11;May 9;June 13...
...

Every four 4 years, the first Tuesday after a Monday in November,
forever (U.S. Presidential Election day):

DTSTART;TZID=America/New_York:19961105T090000
RRULE:FREQ=YEARLY;INTERVAL=4;BYMONTH=11;BYDAY=TU;
BYMONTHDAY=2,3,4,5,6,7,8

==> (1996 9:00 AM EST) November 5
(2000 9:00 AM EST) November 7
(2004 9:00 AM EST) November 2
...

The 3rd third instance into the month of one of Tuesday, Wednesday Wednesday, or
Thursday, for the next 3 months:

DTSTART;TZID=America/New_York:19970904T090000
RRULE:FREQ=MONTHLY;COUNT=3;BYDAY=TU,WE,TH;BYSETPOS=3

==> (1997 9:00 AM EDT) September 4;October 7
(1997 9:00 AM EST) November 6

The 2nd to last second-to-last weekday of the month:

DTSTART;TZID=America/New_York:19970929T090000
RRULE:FREQ=MONTHLY;BYDAY=MO,TU,WE,TH,FR;BYSETPOS=-2

==> (1997 9:00 AM EDT) September 29
(1997 9:00 AM EST) October 30;November 27;December 30
(1998 9:00 AM EST) January 29;February 26;March 30
...

Every 3 hours from 9:00 AM to 5:00 PM on a specific day:

DTSTART;TZID=America/New_York:19970902T090000
RRULE:FREQ=HOURLY;INTERVAL=3;UNTIL=19970902T170000Z
==> (September 2, 1997 EDT) 09:00,12:00,15:00

Every 15 minutes for 6 occurrences:

DTSTART;TZID=America/New_York:19970902T090000
RRULE:FREQ=MINUTELY;INTERVAL=15;COUNT=6

==> (September 2, 1997 EDT) 09:00,09:15,09:30,09:45,10:00,10:15

Every hour and a half for 4 occurrences:

DTSTART;TZID=America/New_York:19970902T090000
RRULE:FREQ=MINUTELY;INTERVAL=90;COUNT=4

==> (September 2, 1997 EDT) 09:00,10:30;12:00;13:30

Every 20 minutes from 9:00 AM to 4:40 PM every day:

DTSTART;TZID=America/New_York:19970902T090000
RRULE:FREQ=DAILY;BYHOUR=9,10,11,12,13,14,15,16;BYMINUTE=0,20,40
or
RRULE:FREQ=MINUTELY;INTERVAL=20;BYHOUR=9,10,11,12,13,14,15,16

==> (September 2, 1997 EDT) 9:00,9:20,9:40,10:00,10:20,
... 16:00,16:20,16:40
(September 3, 1997 EDT) 9:00,9:20,9:40,10:00,10:20,
...16:00,16:20,16:40
...

An example where the days generated makes a difference because of
WKST:

DTSTART;TZID=America/New_York:19970805T090000
RRULE:FREQ=WEEKLY;INTERVAL=2;COUNT=4;BYDAY=TU,SU;WKST=MO

==> (1997 EDT) August 5,10,19,24

changing only WKST from MO to SU, yields different results...

DTSTART;TZID=America/New_York:19970805T090000
RRULE:FREQ=WEEKLY;INTERVAL=2;COUNT=4;BYDAY=TU,SU;WKST=SU

==> (1997 EDT) August 5,17,19,31
An example where an invalid date (i.e., February 30) is ignored.

DTSTART;TZID=America/New_York:20070115T090000
RRULE:FREQ=MONTHLY;BYMONTHDAY=15,30;COUNT=5

==> (2007 EST) January 15,30
(2007 EST) February 15
(2007 EDT) March 15,30

3.8.6. Alarm Component Properties

The following properties specify alarm information in calendar
components.

3.8.6.1. Action

Property Name: ACTION

Purpose: This property defines the action to be invoked when an
alarm is triggered.

Value Type: TEXT

Property Parameters: IANA and non-standard property parameters can
be specified on this property.

Conformance: This property MUST be specified once in a "VALARM"
calendar component.

Description: Each "VALARM" calendar component has a particular type
of action associated with it. which it is associated. This property specifies
the type of action. Applications MUST ignore alarms with x-name
and iana-
token value iana-token values they don't recognize.

Format Definition: This property is defined by the following
notation:

action = "ACTION" actionparam ":" actionvalue CRLF

actionparam = *(";" other-param)

actionvalue = "AUDIO" / "DISPLAY" / "EMAIL"
/ iana-token / x-name
Example: The following are examples of this property in a "VALARM"
calendar component:

ACTION:AUDIO

ACTION:DISPLAY

3.8.6.2. Repeat Count

Property Name: REPEAT

Purpose: This property defines the number of times the alarm should
be repeated, after the initial trigger.

Value Type: INTEGER

Property Parameters: IANA and non-standard property parameters can
be specified on this property.

Conformance: This property can be specified in a "VALARM" calendar
component.

Description: This property defines the number of time times an alarm
should be repeated after its initial trigger. If the alarm
triggers more than once, then this property MUST be specified
along with the "DURATION" property.

Format Definition: This property is defined by the following
notation:

repeat = "REPEAT" repparam ":" integer CRLF
;Default is "0", zero.

repparam = *(";" other-param)

Example: The following is an example of this property for an alarm
that repeats 4 additional times with a 5 minute 5-minute delay after the
initial triggering of the alarm:

REPEAT:4
DURATION:PT5M

3.8.6.3. Trigger
Property Name: TRIGGER

Purpose: This property specifies when an alarm will trigger.

Value Type: The default value type is DURATION. The value type can
be set to a DATE-TIME value type, in which case the value MUST
specify a UTC formatted UTC-formatted DATE-TIME value.

Property Parameters: IANA, non-standard, value data type, time zone
identifier
identifier, or trigger relationship property parameters can be
specified on this property. The trigger relationship property
parameter MUST only be specified when the value type is
"DURATION".

Conformance: This property MUST be specified in the "VALARM"
calendar component.

Description: This property defines when an alarm will trigger. The
default value type is DURATION, specifying a relative time for the
trigger of the alarm. The default duration is relative to the
start of an event or to-do that with which the alarm is associated with. associated.
The duration can be explicitly set to trigger from either the end
or the start of the associated event or to-do with the "RELATED"
parameter. A value of START will set the alarm to trigger off the
start of the associated event or to-do. A value of END will set
the alarm to trigger off the end of the associated event or to-do.

Either a positive or negative duration may be specified for the
"TRIGGER" property. An alarm with a positive duration is
triggered after the associated start or end of the event or to-do.
An alarm with a negative duration is triggered before the
associated start or end of the event or to-do.

The "RELATED" property parameter is not valid if the value type of
the property is set to DATE-TIME (i.e., for an absolute date and
time alarm trigger). If a value type of DATE-TIME is specified,
then the property value MUST be specified in the UTC time format.
If an absolute trigger is specified on an alarm for a recurring
event or to-do, then the alarm will only trigger for the specified
absolute date/time, DATE-TIME, along with any specified repeating instances.

If the trigger is set relative to START, then the "DTSTART"
property MUST be present in the associated "VEVENT" or "VTODO"
calendar component. If an alarm is specified for an event with
the trigger set relative to the END, then the "DTEND" property or
the "DTSTART" and "DURATION " properties MUST be present in the
associated "VEVENT" calendar component. If the alarm is specified
for a to-do with a trigger set relative to the END, then either
the "DUE" property or the "DTSTART" and "DURATION " properties
MUST be present in the associated "VTODO" calendar component.

Alarms specified in an event or to-do which that is defined in terms of
a DATE value type will be triggered relative to 00:00:00 of the
user's configured time zone on the specified date, or relative to
00:00:00 UTC on the specified date if no configured time zone can
be found for the user. For example, if "DTSTART" is a DATE value
set to 19980205 then the duration trigger will be relative to
19980205T000000 America/New_York for a user configured with the
America/New_York time zone.

Format Definition: This property is defined by the following
notation:

trigger = "TRIGGER" (trigrel / trigabs) CRLF

trigrel = *(
;
; the The following are OPTIONAL,
; but MUST NOT occur more than once once.
;
(";" "VALUE" "=" "DURATION") /
(";" trigrelparam) /
;
; the The following is OPTIONAL,
; and MAY occur more than once once.
;
(";" other-param)
;
) ":" dur-value

trigabs = *(
;
; the The following is REQUIRED,
; but MUST NOT occur more than once once.
;
(";" "VALUE" "=" "DATE-TIME") /
;
; the The following is OPTIONAL,
; and MAY occur more than once once.
;
(";" other-param)
;
) ":" date-time
Example: A trigger set 15 minutes prior to the start of the event or
to-do.

TRIGGER:-PT15M

A trigger set 5 five minutes after the end of an event or the due
date of a to-do.

TRIGGER;RELATED=END:PT5M

A trigger set to an absolute date/time. DATE-TIME.

TRIGGER;VALUE=DATE-TIME:19980101T050000Z

3.8.7. Change Management Component Properties

The following properties specify change management information in
calendar components.

3.8.7.1. Date/Time Date-Time Created

Property Name: CREATED

Purpose: This property specifies the date and time that the calendar
information was created by the calendar user agent in the calendar
store.

Note: This is analogous to the creation date and time for a
file in the file system.

Value Type: DATE-TIME

Property Parameters: IANA and non-standard property parameters can
be specified on this property.

Conformance: The property can be specified once in "VEVENT", "VTODO"
"VTODO", or "VJOURNAL" calendar components. The value MUST be
specified as a date with UTC time.

Description: This property specifies the date and time that the
calendar information was created by the calendar user agent in the
calendar store.

Format Definition: This property is defined by the following
notation:

created = "CREATED" creaparam ":" date-time CRLF
creaparam = *(";" other-param)

Example: The following is an example of this property:

CREATED:19960329T133000Z

3.8.7.2. Date/Time Date-Time Stamp

Property Name: DTSTAMP

Purpose: In the case of an iCalendar object that specifies a
"METHOD" property, this property specifies the date and time that
the instance of the iCalendar object was created. In the case of
an iCalendar object that doesn't specify a "METHOD" property, this
property specifies the date and time that the information
associated with the calendar component was last revised in the
calendar store.

Value Type: DATE-TIME

Property Parameters: IANA and non-standard property parameters can
be specified on this property.

Conformance: This property MUST be included in the "VEVENT",
"VTODO", "VJOURNAL" "VJOURNAL", or "VFREEBUSY" calendar components.

Description: The value MUST be specified in the UTC time format.

This property is also useful to protocols such as
[I-D.ietf-calsify-rfc2447bis] [2447bis] that
have inherent latency issues with the delivery of content. This
property will assist in the proper sequencing of messages
containing iCalendar objects.

In the case of an iCalendar object that specifies a "METHOD"
property, this property differs from the "CREATED" and "LAST-
MODIFIED" properties. These two properties are used to specify
when the particular calendar data in the calendar store was
created and last modified. This is different than when the
iCalendar object representation of the calendar service
information was created or last modified.

In the case of an iCalendar object that doesn't specify a "METHOD"
property, this property is equivalent to the "LAST-MODIFIED"
property.

Format Definition: This property is defined by the following
notation:

dtstamp = "DTSTAMP" stmparam ":" date-time CRLF

stmparam = *(";" other-param)

Example:

DTSTAMP:19971210T080000Z

3.8.7.3. Last Modified

Property Name: LAST-MODIFIED

Purpose: This property specifies the date and time that the
information associated with the calendar component was last
revised in the calendar store.

Note: This is analogous to the modification date and time for a
file in the file system.

Value Type: DATE-TIME

Property Parameters: IANA and non-standard property parameters can
be specified on this property.

Conformance: This property can be specified in the "VEVENT",
"VTODO", "VJOURNAL" "VJOURNAL", or "VTIMEZONE" calendar components.

Description: The property value MUST be specified in the UTC time
format.

Format Definition: This property is defined by the following
notation:

last-mod = "LAST-MODIFIED" lstparam ":" date-time CRLF

lstparam = *(";" other-param)

Example: The following is an example of this property:

LAST-MODIFIED:19960817T133000Z

3.8.7.4. Sequence Number

Property Name: SEQUENCE

Purpose: This property defines the revision sequence number of the
calendar component within a sequence of revisions.

Value Type: INTEGER

Property Parameters: IANA and non-standard property parameters can
be specified on this property.

Conformance: The property can be specified in "VEVENT", "VTODO" "VTODO", or
"VJOURNAL" calendar component.

Description: When a calendar component is created, its sequence
number is zero (US-ASCII decimal 48). 0. It is monotonically incremented by the "Organizer's"
CUA each time the "Organizer" makes a significant revision to the
calendar component.

The "Organizer" includes this property in an iCalendar object that
it sends to an "Attendee" to specify the current version of the
calendar component.

The "Attendee" includes this property in an iCalendar object that
it sends to the "Organizer" to specify the version of the calendar
component that to which the "Attendee" is referring to. referring.

A change to the sequence number is not the mechanism that an
"Organizer" uses to request a response from the "Attendees". The
"RSVP" parameter on the "ATTENDEE" property is used by the
"Organizer" to indicate that a response from the "Attendees" is
requested.

Recurrence instances of a recurring component MAY have different
sequence numbers.

Format Definition: This property is defined by the following
notation:

seq = "SEQUENCE" seqparam ":" integer CRLF
; Default is "0"

seqparam = *(";" other-param)
Example: The following is an example of this property for a calendar
component that was just created by the "Organizer":

SEQUENCE:0

The following is an example of this property for a calendar
component that has been revised two different times by the
"Organizer":

SEQUENCE:2

3.8.8. Miscellaneous Component Properties

The following properties specify information about a number of
miscellaneous features of calendar components.

3.8.8.1. IANA Properties

Property Name: An IANA registered IANA-registered property name

Value Type: The default value type is TEXT. The value type can be
set to any value type.

Property Parameters: Any parameter can be specified on this
property.

Description: This specification allows other properties registered
with IANA to be specified in any calendar components. Compliant
applications are expected to be able to parse these other IANA IANA-
registered properties but can ignore them.

Format Definition: This property is defined by the following
notation:

iana-prop = iana-token *(";" icalparameter) ":" value CRLF

Example: The following are examples of properties that might be
registered to IANA:

DRESSCODE:CASUAL

NON-SMOKING;VALUE=BOOLEAN:TRUE

3.8.8.2. Non-standard Non-Standard Properties
Property Name: Any property name with a "X-" prefix

Purpose: This class of property provides a framework for defining
non-standard properties.

Value Type: The default value type is TEXT. The value type can be
set to any value type.

Property Parameters: IANA, non-standard non-standard, and language property
parameters can be specified on this property.

Conformance: This property can be specified in any calendar
component.

Description: The MIME Calendaring and Scheduling Content Type
provides a "standard mechanism for doing non-standard things".
This extension support is provided for implementers to "push the
envelope" on the existing version of the memo. Extension
properties are specified by property and/or property parameter
names that have the prefix text of "X-" (the two character two-character
sequence: LATIN CAPITAL LETTER X character followed by the HYPHEN-
MINUS character). It is recommended that vendors concatenate onto
this sentinel another short prefix text to identify the vendor.
This will facilitate readability of the extensions and minimize
possible collision of names between different vendors. User
agents that support this content type are expected to be able to
parse the extension properties and property parameters but can
ignore them.

At present, there is no registration authority for names of
extension properties and property parameters. The value type for
this property is TEXT. Optionally, the value type can be any of
the other valid value types.

Format Definition: This property is defined by the following
notation:

x-prop = x-name *(";" icalparameter) ":" value CRLF

Example: The following might be the ABC vendor's extension for an
audio-clip form of subject property:

X-ABC-MMSUBJ;VALUE=URI;FMTTYPE=audio/basic:http://www.example.
org/mysubj.au

3.8.8.3. Request Status

Property Name: REQUEST-STATUS

Purpose: This property defines the status code returned for a
scheduling request.

Value Type: TEXT

Property Parameters: IANA, non-standard non-standard, and language property
parameters can be specified on this property.

Conformance: The property can be specified in the "VEVENT", "VTODO",
"VJOURNAL"
"VJOURNAL", or "VFREEBUSY" calendar component.

Description: This property is used to return status code information
related to the processing of an associated iCalendar object. The
value type for this property is TEXT.

The value consists of a short return status component, a longer
return status description component, and optionally a status-
specific data component. The components of the value are
separated by the SEMICOLON character (US-ASCII decimal 59). character.

The short return status is a PERIOD character (US-ASCII decimal
46) separated pair or
3-tuple of integers. For example, "3.1" or "3.1.1". The
successive levels of integers provide for a successive level of
status code granularity.

The following are initial classes for the return status code.
Individual iCalendar object methods will define specific return
status codes for these classes. In addition, other classes for
the return status code may be defined using the registration
process defined later in this memo.

Format Definition: This property is defined by the following
notation:

rstatus = "REQUEST-STATUS" rstatparam ":"
statcode ";" statdesc [";" extdata]

rstatparam = *(
;
; the The following is OPTIONAL,
; but MUST NOT occur more than once once.
;
(";" languageparam) /
;
; the The following is OPTIONAL,
; and MAY occur more than once once.
;
(";" other-param)
;
)

statcode = 1*DIGIT 1*2("." 1*DIGIT)
;Hierarchical, numeric return status code

statdesc = text
;Textual status description

extdata = text
;Textual exception data. For example, the offending property
;name and value or complete property line.

Example: The following are some possible examples of this property.

The COMMA and SEMICOLON separator characters in the property value
are BACKSLASH character escaped because they appear in a text
value.

REQUEST-STATUS:2.0;Success

REQUEST-STATUS:3.1;Invalid property value;DTSTART:96-Apr-01

REQUEST-STATUS:2.8; Success\, repeating event ignored. Scheduled
as a single event.;RRULE:FREQ=WEEKLY\;INTERVAL=2

REQUEST-STATUS:4.1;Event conflict. Date/time Date-time is busy.

REQUEST-STATUS:3.7;Invalid calendar user;ATTENDEE:
mailto:jsmith@example.com

4. iCalendar Object Examples

The following examples are provided as an informational source of
illustrative iCalendar objects consistent with this content type.

The following example specifies a three-day conference that begins at
2:30 P.M. UTC, September 18, 1996 and end ends at 10:00 P.M. UTC,
September 20, 1996.

BEGIN:VCALENDAR
PRODID:-//xyz Corp//NONSGML PDA Calendar Version 1.0//EN
VERSION:2.0
BEGIN:VEVENT
DTSTAMP:19960704T120000Z
UID:uid1@example.com
ORGANIZER:mailto:jsmith@example.com
DTSTART:19960918T143000Z
DTEND:19960920T220000Z
STATUS:CONFIRMED
CATEGORIES:CONFERENCE
SUMMARY:Networld+Interop Conference
DESCRIPTION:Networld+Interop Conference
and Exhibit\nAtlanta World Congress Center\n
Atlanta\, Georgia
END:VEVENT
END:VCALENDAR

The following example specifies a group scheduled group-scheduled meeting that begin begins
at 8:30 AM EST on March 12, 1998 and end ends at 9:30 AM EST on March 12,
1998. The "Organizer" has scheduled the meeting with one or more
calendar users in a group. A time zone specification for Eastern
United States has been specified.

BEGIN:VCALENDAR
PRODID:-//RDU Software//NONSGML HandCal//EN
VERSION:2.0
BEGIN:VTIMEZONE
TZID:America/New_York
BEGIN:STANDARD
DTSTART:19981025T020000
TZOFFSETFROM:-0400
TZOFFSETTO:-0500
TZNAME:EST
END:STANDARD
BEGIN:DAYLIGHT
DTSTART:19990404T020000
TZOFFSETFROM:-0500
TZOFFSETTO:-0400
TZNAME:EDT
END:DAYLIGHT
END:VTIMEZONE
BEGIN:VEVENT
DTSTAMP:19980309T231000Z
UID:guid-1.example.com
ORGANIZER:mailto:mrbig@example.com
ATTENDEE;RSVP=TRUE;ROLE=REQ-PARTICIPANT;CUTYPE=GROUP:
mailto:employee-A@example.com
DESCRIPTION:Project XYZ Review Meeting
CATEGORIES:MEETING
CLASS:PUBLIC
CREATED:19980309T130000Z
SUMMARY:XYZ Project Review
DTSTART;TZID=America/New_York:19980312T083000
DTEND;TZID=America/New_York:19980312T093000
LOCATION:1CP Conference Room 4350
END:VEVENT
END:VCALENDAR

The following is an example of an iCalendar object passed in a MIME
message with a single body part consisting of a "text/calendar"
Content Type.

TO:jsmith@example.com
FROM:jdoe@example.com
MIME-VERSION:1.0
MESSAGE-ID:<id3@example.com>
CONTENT-TYPE:text/calendar; method="xyz"; component="VEVENT"

BEGIN:VCALENDAR
METHOD:xyz
VERSION:2.0
PRODID:-//ABC Corporation//NONSGML My Product//EN
BEGIN:VEVENT
DTSTAMP:19970324T120000Z
SEQUENCE:0
UID:uid3@example.com
ORGANIZER:mailto:jdoe@example.com
ATTENDEE;RSVP=TRUE:mailto:jsmith@example.com
DTSTART:19970324T123000Z
DTEND:19970324T210000Z
CATEGORIES:MEETING,PROJECT
CLASS:PUBLIC
SUMMARY:Calendaring Interoperability Planning Meeting
DESCRIPTION:Discuss how we can test c&s interoperability\n
using iCalendar and other IETF standards.
LOCATION:LDB Lobby
ATTACH;FMTTYPE=application/postscript:ftp://example.com/pub/
conf/bkgrnd.ps
END:VEVENT
END:VCALENDAR

The following is an example of a to-do due on April 15, 1998. An
audio alarm has been specified to remind the calendar user at noon,
the day before the to-do is expected to be completed and repeat
hourly, four additional times. The to-do definition has been
modified twice since it was initially created.

BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//ABC Corporation//NONSGML My Product//EN
BEGIN:VTODO
DTSTAMP:19980130T134500Z
SEQUENCE:2
UID:uid4@example.com
ORGANIZER:mailto:unclesam@example.com
ATTENDEE;PARTSTAT=ACCEPTED:mailto:jqpublic@example.com
DUE:19980415T000000
STATUS:NEEDS-ACTION
SUMMARY:Submit Income Taxes
BEGIN:VALARM
ACTION:AUDIO
TRIGGER:19980403T120000Z
ATTACH;FMTTYPE=audio/basic:http://example.com/pub/audio-
files/ssbanner.aud
REPEAT:4
DURATION:PT1H
END:VALARM
END:VTODO
END:VCALENDAR

The following is an example of a journal entry. entry:

BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//ABC Corporation//NONSGML My Product//EN
BEGIN:VJOURNAL
DTSTAMP:19970324T120000Z
UID:uid5@example.com
ORGANIZER:mailto:jsmith@example.com
STATUS:DRAFT
CLASS:PUBLIC
CATEGORIES:Project Report,XYZ,Weekly Meeting
DESCRIPTION:Project xyz Review Meeting Minutes\n
Agenda\n1. Review of project version 1.0 requirements.\n2.
Definition
of project processes.\n3. Review of project schedule.\n
Participants: John Smith\, Jane Doe\, Jim Dandy\n-It was
decided that the requirements need to be signed off by
product marketing.\n-Project processes were accepted.\n
-Project schedule needs to account for scheduled holidays
and employee vacation time. Check with HR for specific
dates.\n-New schedule will be distributed by Friday.\n-
Next weeks meeting is cancelled. No meeting until 3/23.
END:VJOURNAL
END:VCALENDAR
The following is an example of published busy time information. The
iCalendar object might be placed in the network resource
http://www.example.com/calendar/busytime/jsmith.ifb.

BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//RDU Software//NONSGML HandCal//EN
BEGIN:VFREEBUSY
ORGANIZER:mailto:jsmith@example.com
DTSTART:19980313T141711Z
DTEND:19980410T141711Z
FREEBUSY:19980314T233000Z/19980315T003000Z
FREEBUSY:19980316T153000Z/19980316T163000Z
FREEBUSY:19980318T030000Z/19980318T040000Z
URL:http://www.example.com/calendar/busytime/jsmith.ifb
END:VFREEBUSY
END:VCALENDAR

5. Recommended Practices

These recommended practices should be followed in order to assure
consistent handling of the following cases for an iCalendar object.

1. Content lines longer than 75 octets SHOULD be folded.

2. When the combination of the "RRULE" and "RDATE" properties in a
recurring component produces multiple instances having the same
start DATE-TIME value, they should be collapsed to, and
considered as, a single instance. If the "RDATE" property is
specified as a PERIOD value the duration of the recurrence
instance will be the one specified by the "RDATE" property, and
not the duration of the recurrence instance defined by the
"DTSTART" property.

3. When a calendar user receives multiple requests for the same
calendar component (e.g., REQUEST for a "VEVENT" calendar
component) as a result of being on multiple mailing lists
specified by "ATTENDEE" properties in the request, they SHOULD
respond to only one of the requests. The calendar user SHOULD
also specify (using the "MEMBER" parameter of the "ATTENDEE"
property) of which mailing list they are a member of. member.

4. An implementation can truncate a "SUMMARY" property value to 255
octets, but it MUST NOT truncate the value in the middle of a
UTF-8 multi-octet sequence.

5. If seconds of the minute are not supported by an implementation,
then a value of "00" SHOULD be specified for the seconds
component in a time value.

6. "TZURL" values SHOULD NOT be specified as a file URI type. This
URI form can be useful within an organization, but is problematic
in the Internet.

7. Some possible English values for "CATEGORIES" property include include:
"ANNIVERSARY", "APPOINTMENT", "BUSINESS", "EDUCATION", "HOLIDAY",
"MEETING", "MISCELLANEOUS", "NON-WORKING HOURS", "NOT IN OFFICE",
"PERSONAL", "PHONE CALL", "SICK DAY", "SPECIAL OCCASION",
"TRAVEL", "VACATION". Categories can be specified in any
registered language.

8. Some possible English values for the "RESOURCES" property include
include: "CATERING", "CHAIRS", "COMPUTER PROJECTOR", "EASEL",
"OVERHEAD PROJECTOR", "SPEAKER PHONE", "TABLE", "TV", "VCR",
"VIDEO PHONE", "VEHICLE". Resources can be specified in any
registered language.

6. Internationalization Considerations

Applications MUST generate iCalendar stream streams in the UTF-8 charset and
MUST accept an iCalendar stream in the UTF-8 or US-ASCII charset.

7. Security Considerations

Because calendaring and scheduling information is very privacy-
sensitive, the protocol used for the transmission of calendaring and
scheduling information should have capabilities to protect the
information from possible threats, such as eavesdropping, replay,
message insertion, deletion, modification modification, and man-in-the-middle
attacks.

As this document only defines the data format and media type of text/
calendar that is independent of any calendar service or protocol, it
is up to the actual protocol specifications such as iTIP
[I-D.ietf-calsify-2446bis], [2446bis],
iMIP [I-D.ietf-calsify-rfc2447bis], [2447bis], and
CalDAV "Calendaring Extensions to WebDAV (CalDAV)"
[RFC4791] to describe the threats that the above attacks present, as
well as ways in which to mitigate them.

8. IANA Considerations

8.1. iCalendar Media Type Registration

The Calendaring and Scheduling Core Object Specification is intended
for use as a MIME content type.

To: ietf-types@iana.org
Subject: Registration of media type text/calendar

Type name: text

Subtype name: calendar

Required parameters: none

Optional parameters: charset, method, component component, and optinfo

The "charset" parameter is defined in [RFC2046] for subtypes of
the "text" media type. It is used to indicate the charset used in
the body part. The charset supported by this revision of
iCalendar is UTF-8. The use of any other charset is deprecated by
this revision of iCalendar; however however, note that this revision
requires that compliant applications MUST accept iCalendar streams
using either the UTF-8 or US-ASCII charset.

The "method" parameter is used to convey the iCalendar object
method or transaction semantics for the calendaring and scheduling
information. It also is an identifier for the restricted set of
properties and values that of which the iCalendar object consists of. consists. The
parameter is to be used as a guide for applications interpreting
the information contained within the body part. It SHOULD NOT be
used to exclude or require particular pieces of information unless
the identified method definition specifically calls for this
behavior. Unless specifically forbidden by a particular method
definition, a text/calendar content type can contain any set of
properties permitted by the Calendaring and Scheduling Core Object
Specification. The "method" parameter MUST be specified and MUST
be set to the same value as the "METHOD" component property of the
iCalendar objects of the iCalendar stream if and only if the
iCalendar objects in the iCalendar stream all have a "METHOD"
component property set to the same value.

The value for the "method" parameter is defined as follows:

method = 1*(ALPHA / DIGIT / "-")
; IANA registered IANA-registered iCalendar object method

The "component" parameter conveys the type of iCalendar calendar
component within the body part. If the iCalendar object contains
more than one calendar component type, then multiple component
parameters MUST be specified.

The value for the "component" parameter is defined as follows:

component = "VEVENT"
/ "VTODO"
/ "VJOURNAL"
/ "VFREEBUSY"
/ "VTIMEZONE"
/ iana-token
/ x-name

The "optinfo" parameter conveys optional information about the
iCalendar object within the body part. This parameter can only
specify semantics already specified by the iCalendar object and
that can be otherwise determined by parsing the body part. In
addition, the optional information specified by this parameter
MUST be consistent with that information specified by the
iCalendar object. For example, it can be used to convey the
"Attendee" response status to a meeting request. The parameter
value consists of a string value.

The parameter can be specified multiple times.

The value for the "optinfo" parameter is defined as follows:

optinfo = infovalue / qinfovalue

infovalue = iana-token / x-name

qinfovalue = DQUOTE (infovalue) DQUOTE

Encoding considerations: This media type can contain 8bit
characters, so the use of quoted-printable or base64 MIME Content-
Transfer-Encodings might be necessary when iCalendar objects are
transferred across protocols restricted to the 7bit repertoire.
Note that a text valued property in the content entity can also
have content encoding of special characters using a BACKSLASH
character (US-ASCII decimal 92) escapement technique. This means that content values
can end up being encoded twice.

Security considerations: See Section 7.

Interoperability considerations: This media type is intended to
define a common format for conveying calendaring and scheduling
information between different systems. It is heavily based on the
earlier [VCAL] industry specification.

Published specification: This specification.

Applications which that use this media type: This media type is designed
for widespread use by Internet calendaring and scheduling
applications. In addition, applications in the workflow and
document management area might find this content-type applicable.
The iTIP [I-D.ietf-calsify-2446bis], [2446bis], iMIP
[I-D.ietf-calsify-rfc2447bis] [2447bis], and CalDAV [RFC4791] Internet
protocols directly use this media type also.

Additional information:

Magic number(s): None.

File extension(s): The file extension of "ics" is to be used to
designate a file containing (an arbitrary set of) calendaring
and scheduling information consistent with this MIME content
type.

The file extension of "ifb" is to be used to designate a file
containing free or busy time information consistent with this
MIME content type.

Macintosh file type code(s): The file type code of "iCal" is to
be used in Apple MacIntosh operating system environments to
designate a file containing calendaring and scheduling
information consistent with this MIME media type.

The file type code of "iFBf" is to be used in Apple MacIntosh
operating system environments to designate a file containing
free or busy time information consistent with this MIME media
type.

Person & email address to contact for further information: See the
"Author's Address" section of this document.

Intended usage: COMMON

Restrictions on usage: There are no restrictions on where this media
type can be used.

Author: See the "Author's Address" section of this document.

Change controller: IETF

8.2. New iCalendar Elements Registration

This section defines the process to register new or modified
iCalendar elements, that is, components, properties, parameters,
value data types, and values, with IANA.

8.2.1. iCalendar Elements Registration Procedure

The IETF will create a mailing list, icalendar@ietf.org [2], icalendar@ietf.org, which can be
used for public discussion of iCalendar elements proposals prior to
registration. Use of the mailing list is strongly encouraged. The
IESG will appoint a designated expert who will monitor the
icalendar@ietf.org [2] mailing list and review registrations.

Registration of new iCalendar elements MUST be reviewed by the
designated expert and published in an RFC. A Standard Tracks Standards Track RFC is
REQUIRED for the regisration registration of new value data types that modify
existing properties, as well as for the registration of participation
statuses
status values to be used in "VEVENT" calendar components. A
Standard Tracks
Standards Track RFC is also REQUIRED for registration of iCalendar
elements that modify iCalendar elements previously documented in a
Standard Tracks
Standards Track RFC.

The registration procedure begins when a completed registration
template, defined in the sections below, is sent to
icalendar@ietf.org [2] and iana@iana.org [3]. iana@iana.org. The designated expert is
expected to tell IANA and the submitter of the registration within
two weeks whether the registration is approved, approved with minor
changes, or rejected with cause. When a registration is rejected
with cause, it can be re-submitted if the concerns listed in the
cause are addressed. Decisions made by the designated expert can be
appealed to the IESG Applications Area Director, then to the IESG.
They follow the normal appeals procedure for IESG decisions.

8.2.2. Registration Template for Components

A component is defined by completing the following template.

Component name: The name of the component.

Purpose: The purpose of the component. Give a short but clear
description.

Format definition: The ABNF for the component definition needs to be
specified.

Description: Any special notes about the component, how it is to be
used, etc.

Example(s): One or more examples of instances of the component
needs need
to be specified.

8.2.3. Registration Template for Properties

A property is defined by completing the following template.

Property name: The name of the property.

Purpose: The purpose of the property. Give a short but clear
description.

Value type: Any of the valid value types for the property value
needs need
to be specified. The default value type also needs to be
specified.

Property parameters: Any of the valid property parameters for the
property MUST be specified.

Conformance: The calendar components that in which the property can
appear
in MUST be specified.

Description: Any special notes about the property, how it is to be
used, etc.

Format definition: The ABNF for the property definition needs to be
specified.

Example(s): One or more examples of instances of the property
needs need
to be specified.

8.2.4. Registration Template for Parameters

A parameter is defined by completing the following template.

Parameter name: The name of the parameter.

Purpose: The purpose of the parameter. Give a short but clear
description.

Format definition: The ABNF for the parameter definition needs to be
specified.

Description: Any special notes about the parameter, how it is to be
used, etc.

Example(s): One or more examples of instances of the parameter
needs need
to be specified.

8.2.5. Registration Template for Value Data Types

A value data type is defined by completing the following template.

Value name: The name of the value type.

Purpose: The purpose of the value type. Give a short but clear
description.

Format definition: The ABNF for the value type definition needs to
be specified.

Description: Any special notes about the value type, how it is to be
used, etc.

Example(s): One or more examples of instances of the value type
needs need
to be specified.

8.2.6. Registration Template for Values

A value is defined by completing the following template.

Value: The value literal.

Purpose: The purpose of the value. Give a short but clear
description.

Conformance: The calendar properties and/or parameters that can take
this value needs need to be specified.

Example(s): One or more examples of instances of the value needs need to
be specified.

The following is a fictitious example of a registration of an
iCalendar value:

Value: TOP-SECRET

Purpose: This value is used to specify the access classification of
top-secret calendar components.

Conformance: This value can be used with the "CLASS" property.

Example(s): The following is an example of this value used with the
"CLASS" property:

CLASS:TOP-SECRET

8.3. Initial iCalendar Elements Registries

The IANA is requested to create created and maintain maintains the following registries for iCalendar
elements with pointers to appropriate reference documents.

8.3.1. Components Registry

The following table is to be has been used to initialize the components
registry.

+-----------+---------+------------------------+

8.3.2. Properties Registry

The following table is to be has been used to initialize the properties
registry.

+------------------+------------+---------------------------+

8.3.3. Parameters Registry

The following table is to be has been used to initialize the parameters
registry.

+----------------+---------+-------------------------+

8.3.4. Value Data Types Registry

The following table is to be has been used to initialize the value data types
registry.

+-----------------+---------+-------------------------+

8.3.5. Calendar User Types Registry

The following table is to be has been used to initialize the calendar user
types registry.

+--------------------+---------+------------------------+

8.3.6. Free/Busy Time Types Registry

The following table is to be has been used to initialize the free/busy time
types registry.

+---------------------+---------+------------------------+

8.3.7. Participation Statuses Registry

The following table is to be has been used to initialize the participation
statuses registry.

+--------------------+---------+-------------------------+

8.3.8. Relationship Types Registry

The following table is to be has been used to initialize the property
parameters relationship
types registry.

+-------------------+---------+-------------------------+

8.3.9. Participation Roles Registry

The following table is to be has been used to initialize the participation
roles registry.

+-----------------+---------+-------------------------+

8.3.10. Actions Registry

The following table is to be has been used to initialize the actions registry.

+-----------+------------+--------------------------+

8.3.11. Classifications Registry

The following table is to be has been used to initialize the classifications
registry.

+----------------+---------+--------------------------+

8.3.12. Methods Registry

No values are defined in this document for the "METHOD" property.

9. Acknowledgements Acknowledgments

The editor of this document wish wishes to thank Frank Dawson and Derik
Stenerson, the original authors of RFC2445, RFC 2445, as well as the following
individuals who have participated in the drafting, review review, and
discussion of this memo:

Joe Abley, Hervey Allen, Steve Allen, Jay Batson, Oliver Block,
Stephane Bortzmeyer, Chris Bryant, Tantek Celik, Mark Crispin, Cyrus
Daboo, Mike Douglass, Andrew N. Dowden, Lisa Dusseault, Lars Eggert,
Gren Eliot, Pasi Eronen, Ben Fortuna, Ned Freed, Neal Gafter, Ted
Hardie, Tim Hare, Jeffrey Harris, Helge Hess, Paul B. Hill, Thomas
Hnetila, Russ Housley, Leif Johansson, Ciny Joy, Bruce Kahn, Reinhold
Kainhofer, Martin Kiff, Patrice Lapierre, Eliot Lear, Michiel van
Leeuwen, Jonathan Lennox, Jeff McCullough, Bill McQuillan, Alexey
Melnikov, Aki Niemi, John W. Noerenberg II, Chuck Norris, Mark
Paterson, Simon Pilette, Arnaud Quillaud, Robert Ransdell, Julian F.
Reschke, Caleb Richardson, Sam Roberts, Dan Romascanu, Mike Samuel,
George Sexton, Nigel Swinson, Clint Talbert, Simon Vaillancourt,
Magnus Westerlund, and Sandy Wills.

The editor would also like to thank the Calendaring and Scheduling
Consortium for advice with this specification, and for organizing
interoperability testing events to help refine it.

10. References

10.1. Normative References

[ISO.8601.2004] International Organization for
Standardization, "Data elements and
interchange formats -- Information interchange
-- Representation of dates and times", 2004.

[ISO.9070.1991] International Organization for
Standardization, "Information Technology_SGML
Support Facilities -- Registration Procedures
for Public Text Owner Identifiers, Second
Edition", April 1991.

[RFC2045] Freed, N. and N. Borenstein, "Multipurpose
Internet Mail Extensions (MIME) Part One:
Format of Internet Message Bodies", RFC 2045,
November 1996.

[RFC2046] Freed, N. and N. Borenstein, "Multipurpose
Internet Mail Extensions (MIME) Part Two:
Media Types", RFC 2046, November 1996.

[RFC2119] Bradner, S., "Key words for use in RFCs to
Indicate Requirement Levels", BCP 14,
RFC 2119, March 1997.

[RFC2368] Hoffman, P., Masinter, L., and J. Zawinski,
"The mailto URL scheme", RFC 2368, July 1998.

[RFC3629] Yergeau, F., "UTF-8, a transformation format
of ISO 10646", STD 63, RFC 3629,
November 2003.

[RFC3986] Berners-Lee, T., Fielding, R., and L.
Masinter, "Uniform Resource Identifier (URI):
Generic Syntax", STD 66, RFC 3986,
January 2005.

[RFC4288] Freed, N. and J. Klensin, "Media Type
Specifications and Registration Procedures",
BCP 13, RFC 4288, December 2005.

[RFC4646] Phillips, A. and M. Davis, "Tags for
Identifying Languages", BCP 47, RFC 4646,
September 2006.

[RFC4648] Josefsson, S., "The Base16, Base32, and Base64
Data Encodings", RFC 4648, October 2006.

[RFC5234] Crocker, D. and P. Overell, "Augmented BNF for
Syntax Specifications: ABNF", STD 68,
RFC 5234, January 2008.

[US-ASCII] American National Standards Institute, "Coded
Character Set - 7-bit American Standard Code
for Information Interchange", ANSI X3.4, 1986.

10.2. Informative References

[I-D.ietf-calsify-2446bis]

[2446bis] Daboo, C., "iCalendar Transport-
Independent Transport-Independent
Interoperability Protocol (iTIP)", draft-ietf-calsify-2446bis-09
(work Work
in progress), Progress, April 2009.

[I-D.ietf-calsify-rfc2447bis]

[2447bis] Melnikov, A., "iCalendar Message-Based
Interoperability Protocol(iMIP)",
draft-ietf-calsify-rfc2447bis-05 (work Protocol (iMIP)", Work
in progress), Progress, June 2008.

[ANSI INCITS 61-1986] International Committee for Information
Technology, "Representation of Geographic
Point Locations for Information Interchange
(formerly ANSI X3.61-1986 (R1997))", ANSI
INCITS 61-1986 (R2007), 2007.

[RFC1738] Berners-Lee, T., Masinter, L., and M.
McCahill, "Uniform Resource Locators (URL)",
RFC 1738, December 1994.

[RFC2392] Levinson, E., "Content-ID and Message-ID
Uniform Resource Locators", RFC 2392,
August 1998.

[RFC2397] Masinter, L., "The "data" URL scheme",
RFC 2397, August 1998.

[RFC2425] Howes, T., Smith, M., and F. Dawson, "A MIME
Content-Type for Directory Information",
RFC 2425, September 1998.

[RFC2426] Dawson, F. and T. Howes, "vCard MIME Directory
Profile", RFC 2426, September 1998.

[RFC2445] Dawson, F. and Stenerson, D., "Internet
Calendaring and Scheduling Core Object
Specification (iCalendar)", RFC 2445,
November 1998.

[RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk,
H., Masinter, L., Leach, P., and T. Berners-Lee, Berners-
Lee, "Hypertext Transfer Protocol --
HTTP/1.1", RFC 2616, June 1999.

[RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818,
May 2000.

[RFC4516] Smith, M. and T. Howes, "Lightweight Directory
Access Protocol (LDAP): Uniform Resource
Locator", RFC 4516, June 2006.

[RFC4791] Daboo, C., Desruisseaux, B., and L. Dusseault,
"Calendaring Extensions to WebDAV (CalDAV)",
RFC 4791, March 2007.

[TZDB] Eggert, P. and A. A.D. Olson, "Sources for Time
Zone and Daylight Saving Time Data", January 2007, <http://
www.twinsun.com/tz/tz-link.htm>.

[Note to RFC Editor: Change "A. Olson"
to "A.D. Olson".]
July 2009,
<http://www.twinsun.com/tz/tz-link.htm>.

[VCAL] Internet Mail Consortium, "vCalendar: The
Electronic Calendaring and Scheduling Exchange
Format", September 1996,
<http://www.imc.org/pdi/vcal-10.txt>.

URIs

[1] <mailto:ietf-calsify@osafoundation.org>

[2] <mailto:icalendar@ietf.org>

[3] <mailto:iana@iana.org>

Appendix A. Differences from RFC 2445

This appendix contains a list of changes that have been made in the
Internet Calendaring and Scheduling Core Object Specification from
RFC 2445.

A.1. New restrictions Restrictions

1. The "DTSTART" property SHOULD be synchronized with the recurrence
rule, if specified.

2. The "RRULE" property SHOULD NOT occur more than once in a
component.

3. The BYHOUR, BYMINUTE BYMINUTE, and BYSECOND rule parts MUST NOT be
specified in the "RRULE" property when the "DTSTART" property is
specified as a DATE value.

4. The value type of the "DTEND" or "DUE" properties MUST match the
value type of "DTSTART" property.

5. The "DURATION" property can no longer appear in "VFREEBUSY"
components.

A.2. Restrictions removed Removed

1. The "DTSTART" and "DTEND" properties are no longer required to be
specified as date with local time and time zone reference when
used with a recurrence rule.

A.3. Deprecated features Features

1. The "EXRULE" property can no longer be specified in a component.

2. The "THISANDPRIOR" value can no longer be used with the "RANGE"
parameter.

3. The "PROCEDURE" value can no longer be used with the "ACTION"
property.

4. The value type RECUR no longer allow allows multiple values to be
specified by a COMMA (US-ASCII decimal 44) character separated COMMA-separated list of values.

5. x-name rule parts can no longer be specified in properties of
RECUR value type (e.g., "RRULE"). x-param can be used on RECUR
value type properties instead.

Appendix B. Change Log (to be removed by RFC Editor prior to
publication)

B.1. Changes in -10

A detailed list of changes is available at the following page:
http://tools.ietf.org/wg/calsify/draft-ietf-calsify-rfc2445bis/
draft-ietf-calsify-rfc2445bis-10.changes.html.

a. Addressed IESG evaluation comments and discusses.

b. Clarified that the "RECURRENCE-ID" property MUST have the same
value type as the "DTSTART" property contained within the
recurring component and MUST be specified as a date with local
time if and only if the "DTSTART" property contained within the
recurring component is specified as a date with local time.

B.2. Changes in -09

A detailed list of changes is available at the following page:
http://tools.ietf.org/wg/calsify/draft-ietf-calsify-rfc2445bis/
draft-ietf-calsify-rfc2445bis-09.changes.html.

a. Issue 60: Clarified that multi-valued properties MUST NOT be used
to specify multiple language variants of the same value.

b. Issue 67: Forbid the use of the "DURATION" property in
"VFREEBUSY" components.

c. AD-Issue 1: Added note on most commonly used URI schemes for the
"ALTREP" parameter.

d. AD-Issue 2: Added recommendation on the URI schemes to use for
the "DIR" parameter.

e. AD-Issue 4: Added recommendation for calendar applications that
support importing iCalendar objects.

f. iTIP-APPS-Issue 1: Allowed "DTSTART" to be OPTIONAL for iTIP.

g. iTIP-APPS-Issue 2: Fixed time zone example.

h. iTIP-APPS-Issue 3: Clarified that recurrence instances MAY have
different sequence numbers.

i. iTIP-APPS-Issue 4: Clarified description of the "INTERVAL" rule
part.

j. Modified TSAFE-CHAR to allow HTAB (US-ASCII decimal 9) in TEXT
values.

k. Few editorial changes.

l. Added names to the Acknowledgments section.

B.3. Changes in -08

A detailed list of changes is available at the following page:
http://tools.ietf.org/wg/calsify/draft-ietf-calsify-rfc2445bis/
draft-ietf-calsify-rfc2445bis-08.changes.html.

a. Issue 48: Revert the change to deprecate the "RANGE" parameter.
Only the value "THISANDPRIOR" is deprecated.

b. Issue 81: BYSETPOS: Clarify that "a set" starts at the beginning
of the interval defined by the FREQ rule part.

c. Chair Review: Changed requirement to handle unrecognized CUTYPE
values.

d. Chair Review: Changed requirement to handle unrecognized VALUE
data types.

e. Chair Review: Removed requirements for "DELEGATED-TO" and
"DELEGATED-FROM" to be specified as mailto URI.

f. Chair Review: Added note about alarms from untrusted sources.

g. Chair Review: Added text to clarify the structure of the
document.

h. Chair Review: Added forward reference to the section covering
BACKSLASH character encoding.

i. Removed the text that specifies when the sequence number MUST be
incremented. Text will be added to rfc2446bis.

j. Removed normative reference to RFC2822.

k. Changed reference of RFC4234 to RFC5234.

l. Few editorial changes.

B.4. Changes in -07

A detailed list of changes is available at the following page:
http://tools.ietf.org/wg/calsify/draft-ietf-calsify-rfc2445bis/
draft-ietf-calsify-rfc2445bis-07.changes.html.

a. Issue 8: Clarified how to compute the exact duration of a nominal
duration.

b. Issue 10: Added new examples for "VEVENT" and "VTODO" to
demonstrate that end times are always non-inclusive, that is,
even end times specified as DATE values.

c. Issue 11: Added a table that shows the dependency of BYxxx rule
part expand or limit behaviour on the FREQ value in the rule.

d. Issue 19: Removed section "Registration of Content Type
Elements". Added registration templates in IANA Considerations
section. Specified how applications should treat x-name and
x-token they don't recognize.

e. Issue 65: Removed 3rd recommended practice. Added new
requirements to require "DTEND" and "DUE" to be a local date time
if and only if "DTSTART" is a local date time.

f. Issue 68: Clarified handling of date-times that fall in time
discontinutities.

g. Issue 69: Clarified handling of recurrence instances that fall in
time discontinutities

h. Issue 71: Clarified handling of leap seconds.

i. Issue 75: Clarified that the "RDATE" property MUST be specified
as a local DATE-TIME value in "VTIMEZONE" sub-components.

j. Issue 76: Clarified that the value type of the "DTEND" property
MUST be the same as the "DTSTART" property.

k. Issue 77: Clarified that the value type of the "DUE" property
MUST be the same as the "DTSTART" property.

l. Issue 79: Clarified that "DTSTART" always specify an onset date-
time of an observance and that its value does not need to be
repeated in an "RDATE" property.

m. Issue 80: Rewrote Security Considerations section.

n. Issue 81: Clarified the meaning of "the set of events specified
by the rule" in the description of the BYSETPOS rule part.

o. Modified Abstract section.

p. Moved text of section 2.3 International Considerations at the end
of sectino 2.1 Formatting Conventions.

q. Added Internationalization Considerations section.

r. Modified the description of the following properties: "ATTACH",
"COMMENT", "COMPLETED", "CREATED" "DTSTAMP" "DUE", and "REPEAT".

s. Clarified some differences with ISO 8601.

t. Updated reference to CalDAV and ISO 8601.

u. Updated section "Differences from RFC 2445": added new
restrictions and added list of removed restrictions.

v. Numerous editorial changes.

B.5. Changes in -06

A detailed list of changes is available at the following page:
http://tools.ietf.org/wg/calsify/draft-ietf-calsify-rfc2445bis/
draft-ietf-calsify-rfc2445bis-06.changes.html.

a. Issue 19: Defined new IANA registries. [Work in progress];

b. Issue 23: Clarified that the UNTIL rule part MUST specify a value
of the same type as the value specified by "DTSTART";

c. Issue 27: Clarified how the duration of generated recurrence
instances is determined;

d. Issue 35: Further clarified the description of the "LANGUAGE"
property;

e. Issue 42: Removed the restriction on the values allowed for the
"ACTION" property in the the "VALARM" component;

f. Issue 47: Clarified that alarm triggers relative to a DATE value
type needs to be triggered to 00:00:00 of the user's configured
time zone;

g. Issue 56: Added a note to specify that FREQ MUST be specified as
the first rule part in generated iCalendar applications, but MUST
be accepted in any order to ensure backward compatibility. The
rest of the RECUR value type ABNF has been further simplified;

h. Issue 59: Clarified the default duration of "VEVENT" components
specified with a "DTSTART" property of DATE value type;

i. Issue 61: Modified all the property ABNFs to allow iana-param in
addition to x-param. Also modified the component ABNFs to allow
iana-prop in addition to x-prop. [Work in progress];

j. Issue 62: Removed the text that lead to believe that the
"RECURRENCE-ID" of a specific recurrence instance might change;

k. Issue 64: Clarified that REQUEST-STATUS only allows pairs (1.1)
and 3-tuples (1.1.1).

l. Issue 65: Clarified that a different time zone may be used by
"DTSTART" and "DTEND", and "DTSTART" and "DUE" when specified as
date with local time and time zone reference. [Work in
progress];

m. Issue 66: Clarified that if the "RDATE" property is specified as
a PERIOD, its duration has precedence over the duration of the
recurrence instance defined by the "DTSTART" property;

n. Issue 72: Removed the requirement that a "VTIMEZONE" calendar
component MUST be present if the iCalendar object contains an
RRULE that generates dates on both sides of a time zone shift;

o. Issue 73: Clarified that the "TZID" must be unique in the scope
of an iCalendar object only;

p. Issue 74: Deprecated the "PROCEDURE" value for the "ACTION"
property;

q. Issue 78: Fixed the text to specify that "TZOFFSETFROM" and not
"TZOFFSETTO" must be used with "DTSTART" when generating the
onset date-time values from the "RRULE" in a "VTIMEZONE"
component;

r. Clarified that the "DTSTART" property MUST be specified in a
"VTODO" component when the "DURATION" property is specified;

s. Started to update the time zone information / examples;

t. Numerous editorial changes.

B.6. Changes in -05

A detailed list of changes is available at the following page:
http://tools.ietf.org/wg/calsify/draft-ietf-calsify-rfc2445bis/
draft-ietf-calsify-rfc2445bis-05.changes.html.

a. Fixed ABNF with references in .txt version of the draft;

b. Numerous editorial changes;

c. Clarified that normative statements in ABNF comments should be
considered as normative;

d. Removed notes talking of character sets other than US-ASCII and
UTF-8;

e. Renamed CTL to CONTROL to avoid conflict with the CTL rule
defined in RFC4234;

f. Removed ABNF rules defined in RFC4234;

g. Changed the partstatparam ABNF rule for clarity;

h. Clarified the purpose of negative durations;

i. Added informational references to RFC 2392 (CID URL) and RFC 4516
(LDAP URL).

j. Updated TZDB reference.

B.7. Changes in -04

A detailed list of changes is available at the following page:
http://tools.ietf.org/wg/calsify/draft-ietf-calsify-rfc2445bis/
draft-ietf-calsify-rfc2445bis-04.changes.html.

a. Issue 16: Clarified that recurrence instances, generated by a
recurrence rule, with an invalid date or nonexistent local time
must be ignored and not counted as part of the recurrence set.

b. Issue 26: Clarified how to handle the BYHOUR, BYMINUTE and
BYSECOND rule parts when "DTSTART" is a DATE value.

c. Issue 28: Removed the MUST requirement to specify the "RDATE"
property whenever the duration of a recurrence instance is
modified.

d. Issue 29: Clarified that the "DTSTART" property is REQUIRED in
all types of recurring components.

e. Issue 32: Introduced the notion of an "iCalendar stream" to make
it explicit when we are refering to a "single iCalendar object"
or a "sequence of iCalendar objects".

f. Issue 34: Clarified what should be done with the "method"
parameter when the iCalendar stream is a sequence of iCalendar
objects.

g. Issue 40: Changed to fbprop ABNF rule to specify that the
"DTSTAMP" and the "UID" properties are REQUIRED in "VFREEBUSY"
components.

h. Issue 43: Removed the MUST requirement to specify the "DTSTART"
and the "DTEND" properties as local time in recurring components,
but added a note that in most cases this is the right thing to
do.

i. Issue 44: Changed the x-prop ABNF to allow any parameters on non-
standard properties.

j. Issue 46: Simplified the tzprop, audioprop, dispprop, emailprop,
and procprop ABNF rules by removing the number of required
properties in front of the "*".

k. Issue 48: Deprecated the "RANGE" parameter.

l. Issue 51: Clarified implicit duration of day events with no
"DTEND" nor "DURATION" property.

m. Issue 52: Removed x-name from the "recur" rule part definition.
It should be sufficient to allow xparam on properties of RECUR
value type.

n. Issue 53: Updated the NON-US-ASCII ABNF rule for UTF-8.

o. Issue 56: Changed the "recur" ABNF rule to allow rule parts to be
specified in any order.

p. Issue 57: Specified that the "DURATION" property MUST be
specified as a "dur-day" or "dur-week" value when the "DTSTART"
is a DATE.

q. Issue 58: Changed the jourprop ABNF rule to allow the
"DESCRIPTION" property to occur more than once.

r. Numerous editorial changes.

s. Changed reference to RFC 4646 for Language-Tag.

B.8. Changes in -03

A detailed list of changes is available at the following page:
http://tools.ietf.org/wg/calsify/draft-ietf-calsify-rfc2445bis/
draft-ietf-calsify-rfc2445bis-03.changes.html.

a. Numerous editorial changes.

b. Specified that "DTSTART" should match the pattern of "RRULE" and
is always part of the "COUNT".

c. Specified "RRULE" should not occur more than once in recurring
components.

d. Deprecated "EXRULE".

e. Fixed all ABNF errors reported by Bill Fenner's ABNF parsing web
service available at:
http://rtg.ietf.org/~fenner/abnf.cgi.

f. Changed reference to RFC 4648 for Base64 encoding.

B.9. Changes in -02

A detailed list of changes is available at the following page:
http://tools.ietf.org/wg/calsify/draft-ietf-calsify-rfc2445bis/
draft-ietf-calsify-rfc2445bis-02.changes.html.

a. Numerous editorial changes including the typos listed in the
"RFC2445 Errata":
http://www.rfc-editor.org/cgi-bin/errataSearch.pl?rfc=2445&
and in the "RFC2445 Issues List":
http://www.softwarestudio.org/iCal/2445Issues.html.

b. Clarified line folding requirements.

c. Clarified charset requirements.

d. Clarified line limits requirements.

e. Clarified on the use of the "LANGUAGE" parameter.

f. Fixed the eventprop, todoprop and jourprop ABNF rules with
respect to required properties.

g. Fixed all the examples to use RFC2606-compliant FQDNs.

h. Fixed the Content-ID URLs in the examples.

i. Fixed the LDAP URLs in the examples.

j. Moved multiple references in the Informative References section.

k. Updated the Acknowledgments section.

B.10. Changes in -01

A detailed list of changes is available at the following page:
http://tools.ietf.org/wg/calsify/draft-ietf-calsify-rfc2445bis/
draft-ietf-calsify-rfc2445bis-01.changes.html.

a. Numerous editorial changes (typos, errors in examples, etc.).

b. Fixed invalid media types in examples.

c. Fixed the "DTSTAMP" values in the examples.

d. Moved media type registration in a separate IANA Consideration
section.

e. Added Internationalization Considerations section.

f. Added Security Considerations section.

g. Updated the Acknowledgments section.

Author's Address

Bernard Desruisseaux (editor)
Oracle Corporation
600 blvd. de Maisonneuve West
Suite 1900
Montreal, QC H3A 3J2
CANADA

EMail: bernard.desruisseaux@oracle.com
URI: http://www.oracle.com/